US2265056A - Radio telephone system - Google Patents

Description

Dec. 2, 19M. A. F. BOWERS RADIO TELEPHONE SYSTEM Filed sept. 27, '1940 INVENTOR BYQZOarel/S ATTO of the radio receiver and thereby disables it, while at the same time the lower front contact of the relay SR closes the circuit of the radio transmitter BT. Likewise the middle front contact of the relay SR closes the circuit of the oscillator O so that the carrier current is now supplied to the radio transmitter. By merely manipulating the key K the talker can disable the radio receiver and render the radio transmitter operative while he talks, and upon releasing the key the condition is reversed so that the radio transmitter is disabled and the receiver is placed in operative condition to receive talk coming from the shore station.

As will appear later, this switching operation, with its consequent control of the carrier, is used at the shore station to alternately permit transmission to and from the radio transmitter and radio receiver respectively. This control is effected in such a way that the radio receiver I,

ashore is normally conditioned to receive and the path to the transmitter is disabled. When no carrier is being sent out by the ship station the operator ashore may, by plugging in, condition the transmitter so that the ship may be signaled. If the land station is not calling, however, the receiver ashore will receive the carrier sent out from the ship when its operator actuates the key K to call. After the call has been answered by the shore operator and the carrier sent out from the ship ceases, the normal condition is reversed and the radio transmitter ashore is put in operative condition and the receiver disabled. Thus it is evident that the switching operation between radio transmitter and radio receiver, both aboard ship and on shore, is under the direct control of the key K on shipboard.

The radio transmitting and receiving apparatus ashore is indicated schematically at C. The system illustrated by way of example is a telephone system adapted for communication with ships operating within a limited area such as a harbor, and includes a single radio transmitter ST, which may be of any known type and is illustrated as a simple box. A voice frequency amplifier AT is associated with the radio transmitter ST. This equipment is connected by means of a wire line TL to switching, signaling and controlling apparatus at the marine operators position A and the technical operators position B. Although the ship moves about so that it is in different positions both as to direction and distance with respect to the radio transmitter ashore, it has been found that a single transmitter, located at a xed position, is sufficient for transmission from the shore to a ship at any reasonable location.

Since it is not always possible to use a high power transmitter on board ship, it is desirable to have several receiving stations located at different convenient points along the shore, so that in transmitting from ship to shore the nearest convenient shore receiving station can be used. Consequently at C two radio receivers, SR1 and SR2, are schematically shown. These receivers are of a known type and are therefore illustrated by block diagrams. It will be understood, of course, that more than two radio receivers may be provided if desired. These receivers SR1 and SR2 are connected by means of lines RL1 and RLz, respectively, with the apparatus at the technical operators position.

Each radio receiver ashore is provided with a codan (shown schematically at COD1 and COD2). The codan is of a known type and is therefore shown as a simple block. It receives its name from the fact that it is a carrier operated device which is as unresponsive as possible to noise, the name codan being formed from the initial letters of the phrase carrier operated device antinoise. The normal function of the codan is to insert a high loss in the output of the radio receiver with which it is associated when no carrier signal is being received. As this is a function with which the present invention 1s not concerned, such controlling apparatus, which is well known in the art, is not illustrated.

Each codan is provided with a so-called codan relay illustrated at CR1 in the case of receiver SR1, and at CRz in the case of receiver SR2. The codan relay may have two windings, one of these windings being responsive to a rectied current resulting from the selected carrier, and the other being responsive to a rectiied current resulting from noise. The circuit of the codan which controls the carrier responsive winding may be made sharply selective to the carrier while circuit controlling the noise responsive v winding is made receptive to all frequencies within the side-band range except in the immediate vicinity of the carrier. The result is that the codan relay has its armature thrown in one direction by means of the rectified noise currents when no carrier is being received. When, however, the carrier current comes in and is rectified, the rectified current in the carrier responsive winding of the codan relay causes the latter winding to predominate in its eect over the other winding and swing the armature of the relay to the opposite position. As shown, when the codan relay pulls up in response to the reception of carrier, its armature connects ground to a simplex circuit extending over the line RL1 or RLz as the case may be, connecting the radio receiver to the technical operators position.

The current thus transmitted over the simplex circuit is used at the technical operators position to perform various functions, including the actuation of a signal at the technical operators position. Also it has been the practice, prior to the present invention, to use this current to actuate the signal lamp at the marine operators position A. In accordance with the present invention, however, a relay ISi is included in the simplex circuit operated by the codan relay which establishes an auxiliary circuit (X1 in the case of radio receiver SR1) leading tc the technic-al operators position, where the circuit may be used to effect the setting of a switch under the control of the dial aboard ship, as will be described later.

An example of apparatus for switching, signaling and otherwise controlling the transmission circuits is located at A and B-principally at the latter position. A common transmission path or line L may be provided and this may be switched to a transmitting line TL leading to the radio transmitter ST orto a receiving path RL'leading to a receiving amplifier RA, the input of which accanto is branched to each of .several lines Ria, Bln', etc., leading :to individual radio receivers such as SR1 and SR2. The line L may be optionally switched tothe transmission path or the receiving path RL .under the control of a polar relay. SW, which is under the control .of the push `button K at the ship station D. The transmitting path 'TL may also include a .so-called vogad dor .automatically adjusting the gain of the transmission path ina manner well known in the art, its name being derived 'by using the initials Aof the expression voice .operated .gain adjusting device. 'This device Iis well known and, as it is not concerned with the present invention, is illustrated by 1a conventional box .or rectangle.

As already stated, the .input of the receiving amplified 'RA in the receiving path 'RL may be branched to several transmission paths leading to individual radio receivers. Each of these paths may include an equalizer and pad network of well known type, illustrated at RE1 and 'REa The present invention Ais not concerned with Athe details of these pieces :of equipment and, as they are well known, they are merely rep-resented symbolically.

A polar relay C1 is associated with the path RL1 anda similar relay C2 is associated with the path R112. Each of these relays has a lower .biasing winding. 'The upper winding in each case is connected to the simplex circuit previously described as controlled by the codan relays 1CR1 and CB2. The middle winding 'is .connected to another simplex circuit with which we are not here concerned, Aso that it has `not been illustrated. For purposes of the present invention it is sufficient to know that when the codan relay CB1, for example, connects ground to the sirnplex circuit Yassociated with the upper winding of the polar relay C1, the armature of said relay will be shifted from .its back contact to its front con tact to produce certain .effects `which lwill be .desribed `in more detail later.

Dnc of these eiects is to cause xthe .operationof the technical .operators lamp TOL when 'the carrier (or interference) causes the operation of the codan relay. In systems of the vprior art the actuation .of the relay C1 also energized the signal lamp at vthe marine operators yposition to apprise .the :operator that an incoming call was being made from the ship at D. Since, however, the .codan sometimes operated in response to interference, false signals would -.be received by the marine .operator and to .avoid this the marine operators .call MOL1 and M0112 are actuated by a dial-controlled switching arrange ment about to be described. Whether the lamp M0111 or the lamp MOLZ vis to be used depends upon which .one of the receivers lSR1-or SR2 lis close r.enough to the ship at D to receive its signal.

While .any .suitable dia'lFcontrolled switch may be utilized, the switch herein illustrated -is of the upaand-.arouhd type frequently used in step-bystep automatic .switching systems. vThe switches which control the vlamps MOL1 and MOLe, `respectively, .are separately controlled ythrough the radio receivers SR1 and SR2. As they are identical, however, .only one need be described. The Vswitch Vwhich is controlled from the receiving radio receiver SR1, for example, comprises a wiper W1 shown at position B, 'fwhich, under the control of a vertical stepping magnet "V1, may be stepped vertically to the level `oi any one .of ten banks of contacts, .each having ten contacts in .each bank. 'This action is taken by the switchin response to the *first digit sent by the dial SD at the ship station D.. In response to the' second digit dialed, the wiper W1 will be rotated stepby-step by the 4'rotary magnet R1 to a particular contact inthe vertical row or level to which the wiper has been previously elevated.

As shown, .if the number 5,0 is dialed, the flrst five impulses will elevate the wiper W1 to the fth row of contacls, and the succeeding ten :impulses 'will rotate the wiper to the ytenth contact in that row to complete the circuit .of the marine operators lamp MOL1, thereby indicating that .a call has come in. When the train of carrier waves sent out from 4the ship `'cornes to an end the release :magnet Y1 restores the switch to normal in aweii-kno-wn manner. The stepping ci the .switch is `controlled by relay IT1, connected to an auxiliary circuit Xi leading to the distant radio receiver .SR1 and operated by the relay 151 under the .control of the codan relay CR1. A similar relay IIa, controlling the .switch associated with the path Le, is operated over an auxiliary cir.- cuit Xe lfrom the radio receiver SR2.

The marine .operator is provided with jacks J1 and J2 :for completing the connection in the case of a call signal received from .either of the radio receivers illustrated, it being understood that any desired number of radio receivers may be employed, :in which case there will be an additional jack :or each additional receiver. If the dial .signai 1received 'by the radio receiver SR1 so that the marine operators lamp MOL1 is actuated, the marine operator will plug in to the jack J1. 1f., on'the other hand, the signal is received from the radio receiver the .operator will gc in on the jack J2.

.es soon as the operator plugs in, the sleeve relay .Si is loperated to vdisable the signal lamp. The relay S1 may also provided with an extra Contact `to open the circuit by which relay IT1, operates relay LR1, thus` preventing operation of the switch during conversation. Relay S1 also actuates a secondary relay S2. The latter in conjunction with the polar relay C1 .controls certain switching operations which will be more fully described later. By one of these switching operations 'the Acommon receiving vcircuit RL is extended to the receiving branch path circuit leading to the radio receiver which is receiving the :signal from the ship. Another of these switching operations, which is ultimately con.- tro'lled vhy the push `button K at the ship station, is the switching of the common path L between the transmitting path TL and the receiving path xThe relay 'REC1 completes the .connection from `the .common receiving path RL to the indivdual receiving path `RL1, and the corresponding relay associated with the receiving path R112 will .(in .case .the signal is 'being -received from the 4radio receiver SR2) .connect the common receiving path RL to the individual receiving path R112.

Further .details of .the system 'will be better apprehended from a description of the operation, which is as follows:

Let us suppose that the ship at D is located nearer to the radio receiver SR1 than to the radio receiver SR2. In the normal condition of the circuit the polar relay SW is actuated only by its upper or balancing winding and holds its arma-ture in .such .a position as to close the connection from the common path L to the common receiving vpath RL, .the :transmitting path being disconnected from .the :common path 1L. At the ship station, in .the normal condition of;

the circuit, the push'button K is not actuated and consequently the relay SR is deenergized, so that the radio receiver BR is in receiving condition. When this condition obtains, the' radio transmitter BT is disabled. l

If, now, some one aboard ship desires to telephone, he presses the push button K and operates the dial SD to dial the combination which will operate the marine operators line lamp. In the instance illustrated, this will be accomplished by dialing 50. As soon as the push button is operated the relay SR is energized to open the circuit of the radio receiver BR and close the circuit of the radio transmitter BT.. At the same time it also closes the circuit of the oscillator O to supply the carrier to the radio transmitter. The carrier, upon being transmitted, will be received by the radio receiver SR1 and will operate the codan relay CR1, which in turn completes a circuit through the relay IS1 over the lower side of the path RL1 to the upper winding of the polar relay C1. This causes the polar` relay C1 to shift its armature to its lower contact. This completes a circuit for the relay FL from battery through said relay over the lower back contact of the relay REC1, front contact of polar relay C1, upper back contact of relay REC1, and back contact of relay SCO to ground. Relay FL opens the circuit of normally energized slow release relay T, which completes a circuit through the upper winding of the relay INC. Relay INC completes the circuit for the lamp TOL at the technical operators position.

In circuitsY employed prior to the presentinvention the connection above described was extended also to the marine operator's lamp MOL1. With the circuit wired in accordance with the present invention, any condition that operates the codan relay CR1 will operate the lamp TOL at the technical operators position, whether it be the ship calling or an interfering condition, but the marine operators lamp MOL1 will not be operated.

In accordance with the present invention, it is necessary for the caller at D to do something more than merely press the key K in order to call the marine operator at A. After depressing the key K the caller must next operate the dial SD to interrupt the carrier in accordance with a code. In the present instance it will be assumed that the code dialed is 50. This will first interrupt the carrier ve times. The fifth interruption is followed by a spurt of carrier, and then the carrier is interrupted ten times in succession. It will be noted that when the carrier is sent out by depressing the key K, the codan relay CE1 operates the relay IS1. This in turn completes a circuit from ground over the front contact of said relay and over the conductor X1 (which may be a simplex circuit derived from a spare pair), and through the winding of the relay IT1 to battery. Relay IT1 completes a circuit f'or the pulsing relay LR1, which at its front contact completes a circuit for the slow release relay D1, which will be held up during interruptions of the carrier due to dialing. A circuit is prepared for the vertical magnet V1 over the front contact of the slow release relay D1, but this circuit is not completed so long as the carrier remains uninterrupted.

When the dial SD is operated, the first interruption of the carrier causes a momentary release of the relay IS1 at C, with the consequent release of the relay I'Ii at B. The armature of the pulsing relay LR1 falls oi and completes a circuitover` its back contact from ground, overthe front contact of slow release relay D1, over the normal left-hand contact of the off-normal switch ON, through slow release relay D1 and through the vertical relay V1 to battery. The pulse vthrough the vertical magnet V1 lifts the wiperl W1 one step, bringing it on a level with the rstrow of contacts. At the end of the impulse the armature of the pulsing relay LR1 is again drawn up and is followed by the second interruption of the carrier, which again causes the armature of relay LR1 to fall back and complete a circuit from ground over the back contact of said relay, over the front contact of the relay D1 and over the left-hand alternate contact of the oli-normal switch (ON), and thence over the front contact of slow release relay D1', through the winding of relay D1 and through the vertical magnet V1 to battery. This second pulse through the vertical relay elevates the wiper W1 another step. It will be noted that the pulsing circuit for the vertical magnet V1 is now completed over the front contact of the slow release relay D1', which remains energized during pulsing interruptions of the carrier. Successive interruptions of the carrier in dialing the digit 5 send additional pulses over the back contact of the pulsing relay LR1 and through the vertical magnet V1, over the circuit just described, thus stepping the wiper W1 to the fifth row of contacts of the switch.

At the end of the iifth interruption the carrier is transmitted for a longer time than during the periods between dialing impulses and this permits the slow release relay D1 to fall oi so that its armature is on its back contact. When the caller at station D dials the first interruption of the ten impulses representing zero, the first interruption causes the pulsing relay LR1 to fall oi as before. This time it completes a circuit from ground, over the front contact of the slow release relay D1, over the left hand alternate contact of the olf-normal switch ON, over the back contact of the slow release relay D1', through the slow release relay D1 and through the rotary magnet R1 to battery. The slow release relay D1 opens the circuit from battery to the wiper W1 during the rotary stepping operation and holds it open until the end of the series of interruptions due to dialing. This irst impulse through the rotary magnet R1 steps the wiper W1 horizontal to the first contact in the fth row, and successive interruptions of the carrier, due to dialing, successively advance this wiper horizontally until it rests upon the last contact of the fifth row.

At the end of the dialing operation the slow release relay D1 falls olf and a circuit is completed from battery over the back contact of said relay, over the wiper W1 and the tenth contact in the fth row, and over the back contact of the relay S1 to the lamp MOL1, causing the lamp to glow to apprise the marine operator that a call has come in. If desired another lamp, located at the technical operators position, may be used in parallel with the lamp MOL1 beyond armature of relay S1, so that the technical operators position will be signalled also by this dialing operation. It will be noted that the slowy release relay D1 is maintained energized from the time the carrier is applied at station D through all of the momentary interruptions due to dialing, until such time as the carrier is interrupted by releasing the key K.

As soon as the marine operator notes that the lamp MOL1 is glowing, she knows that a call has come in through the radio receiver SR1. Of course, had the call come in through the radio receiver station SR2, the dialing operation would have actuated the wiper W2 associated with the circuit L2 and would have caused the lamp MOLz to glow, which would have indicated a call from the radio receiver SR2. The operator now plugs into the jack J1, thus operating the relay S1 over the sleeve circuit. At its left-hand armature the relay S1 opens the circuit of the signal lamp MOL1 and at its right-hand front contact it completes a circuit through the relay S2.

Relay Se at its upper front contact completes a circuit from ground through the winding of relay REC1 which at its upper contact extends the circuit RL to the branch circuit RL1 leading to the output of radio receiver SR1. At its middle contact relay REC1 shifts the ground connection for the armature of the polar relay C1 from the back contact of the relay SCO to the front contact of the middle armature of relay REC1. `At its lower front contactrelay REC1 opens the circuit of relay FL which, acting through relays T and INC, opens the circuit of the lamp TOL at the technical operators position. The lower armature of the relay REC1 at its front contact completes the circuit from ground over its middle front contact, over the front contact of the polar relay C1 (carrier now being received so that this relay is actuated), over the lower front contact of relay REC`1, and through the winding of relay SCO, which latter relay is operated.

This condition obtains so long as the push butvton K is actuated by the caller at station D. Consequently, from the time the operator answers the call at jack J1 until the push button is released the relay REC1 maintains a connection from the common receiving circuit RL, over' the upper front contact of the relay REC1, to the receiving circuit RL1 connected to the radio receiver SR1 at station C. The relay corresponding to REC1, associated with the receivingy circuit RLz is not actuated, and consequently the latter circuit is not connected to the common receiving circuit RL. It will also be noted that the circuit through the lower winding of the polar relay SW is held open by the polar relay C1 because its armature is on its front contact so long as the carrier persists. Consequently, the radio receiver SR1 is during this period connected over the receiving circuit RL1 through the equalizer pad RE1 over the upper front contact of the relay REC1, through the receiving amplifier RA, over the common receiving circuit RL, and over the lower or front contact of the polar relay SW, and thence over the common circuit L to the branch L1 o'i said circuit leading to the jack J1. The operator is now able to hear anything said by the caller at station D.

In order that the caller at station D mayv know that the operator' is asking him for information as to the connection desired, he mu'st, as' soon as he has dialed the operator, release the push button K, thus disabling his transmitter BT and putting his radio receiver BR in operatingv position. This is done throughl the release of the relay SR. The consequent interruption of the carrier at the radio transmitter BT causes the codan relay CR1 to fall off and release the relay S1V at C and open the circuit through the upper winding of the polar relay' Cr at B1 Polar relay C1 now shifts its armaturev to its upper back contact and thereby completes a circuit from ground over the middle front contact of relay REC1, over the upper contact of the polar relay' C1, over the lower contact of relay S2, and through the lower winding of the polar relay SW to battery. This shifts the armature of the polar relay from its lower contact to its upper contact, thereby opening the receiver connection through RL and completing the connection from the jack J1, over the circuit L1, common circuit L, and over the transmitting circuit TL to the radio transmitter ST. The operator is now able to talk. to the caller at D from the radio transmitter ST through the radio receiver BR.

The release ci the relay IS1, just referred to, and which resulted from the release of the key K at D, disconnects ground from the circuit X1 and thereby causes the release of the relay IT1. This in turn releases the pulsing relay LR1, whose armature is restored to its back Contact, and as rsoon as the slow release relay D1 releases, a circuit is completed from ground over the back contact of the pulsing relay LR1, over the back contact of the relay D1, over the right-hand contact of the oli-normal switch ON, through the release magnet Y1 to battery. The release magnet now restores the switch wiper W1 to normal so that switching apparatus is now ready to respond to a new rdialing operation.

The caller at D, having heard the operator challenge his call, now pushes the button K, with the result that the relay SR disables his radio receiver BR and applies carrier to his radio transmitter. This operates the codan relay CR1, and again completes the circuit from ground through the relay IS1 and over the simplex circuit of the pair RL1, through the upper winding of the polar Yrelay C1. Polar relay C1 now shifts its armature to its lower or front position and this opens the circuit of the lower winding of the polar relay SW. The relay SW accordingly shifts its armature to its lower contact and the 'circuit from the jack J1 isnow shifted from the transmitting line TL tothe receiving line RL1 and the caller is able to talk to the operator.

After the operator has completed the connection the caller may talk to the party with whom he is connected by operating the key K to transmit the carrier and releasing the key whenever he wishes to hear the response of the called party.

The relay REC1 of course remains operated so long as the connection is established at the jack J1. When the called party hangs up his receiver, the operator may receive'a disconnect signal and withdraw the plug from the jack J1; This releases the relay S1, which in turn releases the relay S2. Relay S2, upon being restored to normal, opens the circuit of the relay REC1, which releases and opens the circuit of relay SCO so that the apparatus is restored to normal.

It will, or course, be evident that when no call isbeing sent out from the ship station at D and with the apparatus at stations A and B in normal condition, the circuit L will be conditioned to receive, as the lower winding of the polar relay SW will'be open-circuited at the contacts of the relay S2 and corresponding relays. The biasing winding of said relay SW will therefore pull the armature to its lower contact, completing the circuit from the path L to the path RL. Under these conditions the marine operator at A may at any time signal thev ship by plugging into the jack J1, thus energizing relays S1 and Sa in succession, so that a circuity is completed from ground over the back contact of relay SCO, over the middle back contact of the polar relay C1, the upper or back contact of the polar relay C1, and over the lower front contact of relay S2 through the lower winding of the polar relay SW. The current through the lower Winding of the polar relay SW will shift its armature so that the path L will be connected to the transmitting path TL. The operator may now signal over the path TL by signaling equipment (not shown) and can, of course, talk over said path and through the radio transmitter ST at station C and radio station BR at station D in an obvious manner.

The dial equipment at ship station D and the step-by-step switching equipment at station B may be utilized for other purposes than those already described. For example, with the circuit as shown, the ship operator can send a signal to indicate dangers to navigation by dialing 80. This will cause the wiper W1 (or W2 as the case may be) to be elevated to the eighth row of contacts and stepped around to the tenth contact in that row, thus completing a circuit for the lamp DNL at the technical operators position, and, if desired, other lamps may be connected to the same circuit located at other positions where it is desired that this signal shall appear. An urgent call may be indicated by dialing 07, which requires ten interruptions and will step the switch wiper W1 to the tenth row, and the seven impulses following will step it around to the seventh contact in that row, completing the circuit in the urgent call lamp UCL. This lamp, and other lamps on the same circuit may be wired to appear at any desired point. A distress call may be made by dialing 03, in which case the wiper W1 will be stepped up in the tenth row and the third contact in that row, completing the circuit of the distress call lamp DCL, which likewise may be wired to appear at any desired point. If it is desired to dial the technical operator directly without calling the marine operator a lamp TOL' may be actuated by dialing the code 70, for example.

Instead of lamps it will be understood that audible signals such as gongs may be used, or if preferred, both gongs and lamps may be employed.

What is claimed is:

1. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when. the carrier frequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at the common terminai of said land station, and means to interrupt the carrier from the ship station in accordance with a code, said supervisory signal device at said common terminal being actuated only in response to said code.

2. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship station or from an interfering station to produce a signal at the land station, a supervisory signal device at the common terminal of said land station, means to interrupt the carrier from the ship station in accordance with a code, and means at the land station responsive to the code but unresponsive to interference to actuate said supervisory signal device at said common terminal.

3. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received from the ship station, and operable when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship station or from an interfering station to produce a signal at the land station, a supervisory signal device at the common terminal of said land station, means at the ship station to interrupt the carrier sent out from the ship station in accordance with a code, a selective arrangement at the land station arranged to actuate said supervisory signal in response to the carrier frequency from the ship when interrupted in accordance with a particular code, but not actuating said signal in response to steady carrier, or carrier interrupted by a different code, or in response to interference.

4. -In a ship shore radio telephone system, a land radio station having Aa normally disabled radio transmitter and a plurality of radio re.- ceivers each normally conditioned for operation, a short controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to said land circuit, a ship station having a normally disabled radiotransmitter Yand a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means conditioned by the extension of a connection to a land circuit through said controlling and switching point to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so conditioned to disable all of said radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at said switchingpoint, and means to interrupt the carrier from the ship station in accordance with a code to actuate said supervisory signal device at said switching point.

5. In a ship shore radio telephone system, a land radio station having a normally disabled radio transmitter .and a plurality of radio receivers each normally conditioned for operation, a shore controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means conditioned by the extension of a connection to a land circuit through said controlling and switching point to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so conditioned to disable all of said radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a signal means at the land station responsive to a current of carrier frequency from the ship station or from an interfering station to produce a signal at the land station, a supervisory signal device at said switching point, means to interrupt the carrier from the ship station in accordance with a code, and means at the land station responsive to the code but unresponsive to interference to actuate said supervisory signal device at said switching point.

6. In a ship shore radio telephone system, a land radio station having a normally disabled radio transmitter and a plurality of radio receivers each normally conditioned for operation, a shore controlling and switching point at which connections may be completed from a land circuit t/o said transmitter and from any of said receivers to said land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means conditioned by the extension of a landward connection to a land circuit through said controlling and switching point to--maintain the radio transmitter at the land station in disabled condition only when the .carrier frequency is being received by one of said radio receivers .at the land station, and operable only when so conditioned to disable the radio receivers at the land station and .condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station,a signal lmeans at the land station responsive to a current of carrier frequency from the ship stationv or from an interfering station to produce a signal at the land station, a supervisory signal device at said switching point, means at the ship station to interrupt the carrier sent out from the ship station in accordance. with a code, a selective arrangement at the 'land station arranged to actuate said supervisory signal device in response to the carrier frequency from the ship when interrupted in accordance with a particular code, but not actuating said signal in' response to steady carrier, or carrier interrupted by a different code, or in response to interference.

7. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection from the common terminal of said land. radio station to a land circu't to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at the common terminal of said land station, means to interrupt the carrier from the ship station in accordance with a code, and means at the land station responsive to the code but unresponsive to interference to actuate said supervisory signal device at said common terminal.

8. In a ship shore radio telephone system, a land radio station having paths from a common terminal to a normally disabled radio transmitter and to a radio receiver normally conditioned for operation, means operable at will to extend said common terminal to a land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier wave, means at said land station conditioned by the extension of a connection Afrom the common terminal of said land radio station to a land circuit to maintain the radio transmitter at the land station in disabled condition only when the carrier Vfrequency is being received from the ship station, and operable only when so conditioned to disable the radio receiver at the land station and to condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at the common terminal of said land station, means at the ship station to interrupt the carrier sent out from the ship station in accordance with a code, a selective arrangement at the land station arranged to actuate said supervisory signal in response to the carrier frequency from the ship when interrupted in accordance with a particular code, but not actuating said signal in response to steady carrier, or carrier interrupted by a different code, or in response to interference.

9. In a ship shore radio telephone system, a land radio station having a normally disabled radio transmitter and a plurality of radio receivers each normally conditioned for operation, a shore controlling and switching point at which connections may be completed from a land circuit to said transmitter and from any of said receivers to said land circuit, a ship station having a normally disabled radio transmitter and a radio receiver normally conditioned for operation, means at said ship station to disable the radio receiver thereat and to condition said radio transmitter at the ship station to send out a carrier Wave, means conditioned by the extension of a connection to a land circuit through said controlling and switching point to maintain the radio transmitter at the land station in disabled condition only when the carrier frequency is being received by one of said radio receivers at the land station, and operable only when so conditioned to disable all of said radio receivers at the land station and condition the radio transmitter thereat for operation when no carrier is transmitted from the ship station, a supervisory signal device at said switching point, means to interrupt the carrier from the ship station in accordance with a code, and means responsive to the code but unresponsive to interference to actuate said supervisory signal device at said switching points.

ALBERT FRANKLIN BOWERS.

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