US2045146A - Communication system - Google Patents

Communication system Download PDF

Info

Publication number
US2045146A
US2045146A US659032A US65903233A US2045146A US 2045146 A US2045146 A US 2045146A US 659032 A US659032 A US 659032A US 65903233 A US65903233 A US 65903233A US 2045146 A US2045146 A US 2045146A
Authority
US
United States
Prior art keywords
station
signal
subscribers
relay
predetermined
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US659032A
Inventor
Howard T Jeandron
Adelbert R Morton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Western Electric Co Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Western Electric Co Inc filed Critical Western Electric Co Inc
Priority to US659032A priority Critical patent/US2045146A/en
Application granted granted Critical
Publication of US2045146A publication Critical patent/US2045146A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M15/00Arrangements for metering, time-control or time indication ; Metering, charging or billing arrangements for voice wireline or wireless communications, e.g. VoIP
    • H04M15/08Metering calls to called party, i.e. B-party charged for the communication

Definitions

  • FIG. 1 A first figure.
  • This invention relates to communication systems and more particularly'to" a system in which a central office" is' enabled to secure an identificatory response from an idle or unattended subscribers telephone by the use of a predetermined code signal.
  • A- characterizing object of the invention is the provision of means whereby a predetermined signal sent from one station to another will automatically evoke a responsive signal in return which uniquely and predetermined'ly identifies or is characteristic of the second station.
  • Fig. 3 is a variated diagram ofapart of the arrangement shown in Fig ⁇ 2 to: illustrate the scope of variability of the latter.-
  • the actuation of the relay 52 alsopermits current from the battery 32 to fiow through the 5 solenoid 54 and lift the plunger 55' breaking the contact at l3 and-lifting the dasher of the dash-- pct 56.
  • the dash pot and the successive pulses of current keep the contactat l3 broken untilafter the predetermined number oi pulses 40 operated the selector 43 and sufficient time has elapsecltoallow the operatorto note the bridging of the-line wires- 4-] and ⁇ 12 by the resistance
  • the stem 55 sinks gradu ally into the dash pot until the contact at 13 45 at B. He calls the operator at A in the usual manner and states his desire and gives his secret code number, in this case the number four.
  • the operator closes the contact at I0 and waits for a response and an authorization to make the charge from B. Receiving no answer, the operator opens the contact at I0 and closes that at I2 and operates the interrupter II to send four pulses. The above described process takes place and the operator receives the same signal from the line as though the receiver at B had been lifted. This response to the code number is taken as authority to make the charge.
  • FIG. 2 illustrates another embodiment of the invention as applied to a four party line with the customary selective ringing installation.
  • the customary apparatus for one of the four subscribers is indicated generally by the letter K from which the party line wires MI and I42 lead to a central station jack indicated generally by the number I20.
  • the usual A. C. ringing generator I3I working through the biasing batteries I33 and I34 supplies combined alternating and direct current to the wires I44 and I45 and thence through apparatus to be described to the jack I20 and so to the line wires MI and I42.
  • the usual operators set connected to the jack I20 is generally indicated at 0.
  • the operator closes the contacts II2 closing a circuit from the battery I 38 to actuate the relays I5I and I50.
  • Alternating current from the generator I3I and direct current from the battery I34 then flow through the wire I45 and the lower contacts of relay I5I.
  • the alternating current passes thence via condensers I9I and I93, lower contacts of relay I 50, jack I20, line wire I4I, condenser I94, relay winding I 55, line wire I42, tip side of jack I20, upper contacts of relay I50, condensers I92 and I90, and upper contacts of relay I5I to ground.
  • This current operates relay I closing a circuit for the direct current.
  • the direct current passes from the lower contacts of relay I5I through inductive -resistance I8I, relay windings I61, I68, I69, and
  • relay I10 lower contacts of relay I50, jack I20, line wire I4I, button switch II6, contacts of relay I55 (closed now by the alternating current), and winding of relay I59 to ground.
  • This current operates relay I59 and tends to operate polarized relays I61 and I68 but not polarized relays I69 and I10.
  • This actuation of relay I59 allows current from battery I35 to pass via relay I59, line I42, jack I20, upper contacts of relay I50, windings of relays I63, I64, I and I66, inductive resistance I80, and upper contacts of relay I5I to ground, thus tending to actuate polarized relays I63 and I64 but not polarized relays I65 and I66.
  • Battery I32 is connected at one side to ground and at its other side to the leads of the windings of the two sets of relays I63, I64, I65, I66 and I61, I68, I69, I10. Batteries I34 and I32 and windings I61, I68, and I59 are so balanced against each other that in the case now being considered the combined effect of the two batteries is surficient to operate relay I68 but not relay I61. Also batteries I34, I32, and I35, resistance I82, and windings of relays I63 and I64 are so chosen that their combined efiect will operate both relays I53 and I64.
  • Closing of relays I63, I64, and I68 closes a three branched circuit from battery I31, through lamps D, C, and F in parallel, and the contacts of relays I63, I64, and I68 in parallel to ground, thus lighting lamps CDF and confirming the code identification given by the subscriber.
  • relay I56, I51 and I58 as well as relay I55 from line wire I4I to line wire I42 and will operate these relays, but relay I60 is polarized against direct current from line wire I 4
  • relay I59 of this group will be actuated and only subscribers set K to which relay I59 is assumed to belong will respond with its characteristic identificatory signal.
  • the button switches H6, H1, H8, and H9 are included merely for convenience to enable the subscriber to dispense with this service if he so wishes.
  • I I3 or II4 will bring a unique response from the bank of signa1 lamps in each case.
  • a code sign and its corresponding signal may be changed for any one subscriber by changing the resistance I82, I83, I84 or I85 as the case may be, by adding or removing a battery I35 or I36, by changing the relay I59, I60, I6I or I62 respectively, by inverting the connections to the line wires MI and I 42, etc.
  • Fig. 3 illustrates twenty-four difierent arrangements of the signal circuit closing relay with resistances of only two difierent sizes available and with or without a battery. Thus a great variety of possible code signals is available for assignment to any one subscriber.
  • the invention as herein shown is illustrated as combined for use with a hand operated central station, it may obviously also be combined with the supervising operators position of an automatically operating central station since in no case is the construction or mode of operation of the central station involved.
  • the invention is not limited to application to telephone systems but by suitable modification in detail may be applied to any communication systems in which messages are transmit ted electrically between two or more stations.
  • a first station a second station, electrical means to transmit a call signal from the first station to the second station, and electrical means for transmitting messages therebetween, in combination with means at the first station to transmit a predetermined signal distinct from the call signal to the second station, and means at the second station responsive only when the second station is idle to the predetermined signal to return to the first station a predetermined signal.
  • a first station a plurality of second stations, electrical means to transmit a call signal from the first station to any second station, and electrical means for transmitting messages therebetween, in combination with means at the first station to transmit a predetermined signal to any one of the second stations different from the call signal of that second station, and means at the particular second station responsive only when the second station is idle to the predetermined signal to return to the first station a predetermined signal.
  • a first station In a communications system, a first station, a plurality of second stations, and electrical means for transmitting messages therebetween, in combination with means at the first station to transmit to the second stations any one of a set of predetermined signals each uniquely pertaining to one second station, means at each second station responsive only to the signal pertalning to that station to return to the first station a predetermined signal characteristic of the said particular second station, and means at the first station consisting of a plurality of lamps, operable by each predetermined return signal, to show a code characteristic of the said particular second station.
  • a central station In a telephone system, a central station, a subscribers station, electrical means at the central station to transmit a call signal to the subscribers station, and electrical means for transmitting messages therebetween, in combination with means at the central station to transmit a predetermined signal different from the call signal to the subscribers station, and means at the subscribers station responsive only when the subscribers station is idle to the predetermined signal to return to the central station a predetermined signal.
  • a central station a plurality of subscribers stations, electrical means to transmit a call signal from the central station to anyone of the subscribers stations, and electrical means for transmitting messages therebetween, in combination with means at the central station to transmit a predetermined signal different from the call signal to any one of the subscriber's stations, and means at the particular subscribers station responsive only when the particular subscribers station is idle to the predetermined signal to return to the central station a predetermined signal.
  • a central station in combination with means at the central station to send to the subscribers station an electrical signal of predetermined sign and character and comprising a direct current component and an alternating current component, means at the subscribers station responsive to and actuable only by the electrical signal of predetermined sign and character to return to the central oflice a responsive electrical signal of predetermined sign and character, and. further means at the central station actuable only by the responsive signal to identify the subscribers station responding.
  • a central office and a plurality of subscribers stations electrically connected thereto in combination with means at the central station to send simultaneously to a group of the subscribers stations any one of a variety of electrical signals each of predetermined sign and character and comprising a direct current component and an alternating current component, means at each of several of the group of subscribers stations responsive to and actuable by one and only one of the variety of electrical signals to return to the central station a responsive electrical signal characteristic and identificatory of the responding subscribers station, and further means at the central station actuable by the responsive signal to give an indication identifying the responding station, no two subscribers stations in any one group having means responsive to the same signal.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Description

FIG.
' H. T. JEANDRON ET AL COMMUNICATION SYSTEM Filed March 1, 1933 3 Sheets-Sheet l INVENTORS H. T. JEA/VDRON A. R. MORTON ATTORNEY June 23, 1936- H. T. JEANDRON ET AL 2,045,145
COMMUNICATION SYSTEM Filed MaICh 1, 1933 3 ShGtS-ShSGt 2 INKENTORS H. 7'. JEANDRON .4. P. MORTON 23 3 k h .wQ wt S m3 13 F n 5 d. KE 5 M I A 1. at mm QMWMZ NS W1 J a@ 52: 7 v v.2 m9 P2 o NE H A TTORNEY 31mm .1935- H. T. JEANDRON ET AL. 2
COMMUNICATION SYSTEM Filed March 1, 1953 3 Sheets-Sheet 3 A TTORNEV Patented June 23, 1936 PATENT OFFICE;
COMMUNICATION SYSTEM Howard T. Je'andron, Hacketts'town, N. J., and Adelbert. R. Morton, Brooklyn, N. Y., assignorsto Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 1, 1933. SerialNo. 659,032
8 Claims.
This invention relates to communication systems and more particularly'to" a system in which a central office" is' enabled to secure an identificatory response from an idle or unattended subscribers telephone by the use of a predetermined code signal.
It may happen that a telephone subscriber away from his'own telephone and using, perhaps; a' pay station instrument may wish to charge a toll call to his own home account. In such'cases' it is customary in some instancesfor the" central ofiiceto' make an independent call to the subscribers private number and thus" obtain verification before completing the call desiredby the subscriber at the public-telephone. If n'o-answer isobtained from the subscribers private telephone the verification cannot be made; I
A- characterizing object of the invention is the provision of means whereby a predetermined signal sent from one station to another will automatically evoke a responsive signal in return which uniquely and predetermined'ly identifies or is characteristic of the second station.
It will be evident that althoughthe invention is'herein disclosed as pertaining to and embodied in a wire telephone system it is'characteristically capable-of being employed with and" embodied in any system of communications, wherein electrical means are-used to transmit messages and where'- in it is desired to evoke from a" distant station an automatic response which will identify the automatically responding station.
Other objects and. characteristic features of the invention will appear from the detailed de-' scription below taken together'with the append? ed" drawings in which Fig. 1 is a diagram of a manual= telephonecircuit showing one embodimentof the invention for the use of a one subscriberprivate telephone connected to a manual central oifice';
Fig; 2iis azsimilardiagram or another'embodi ment of the same, and
' Fig. 3 is a variated diagram ofapart of the arrangement shown in Fig} 2 to: illustrate the scope of variability of the latter.-
In= carrying out theinventionas herein shown and referring now to Fig; I; there is employed the customary manual central oflic'e apparatus generally indicated by the letter A; t-heusual sukiscrlbers telephone set" generally indicated by the letter'lk;v and the novel auxiliary" apparatus generally indicated by the letter C;
The parts of the apparatus A and B' are old andwell'known and will not he further described or'particularized than necessaryto showth'e' application' and connection thereto of apparatus" 0.
In the embodiment shown in Fig. 1 the customary central ofii'ce' ringing: contacts are shown at It. When contact i's made at H!" current from the battery 30 passes through the wire W to ground and operates therelay5u-permittingnng ing pulses from the generatorsl and'interrupter" H to pass as usual over" the line wires H and 42 to the subscribers set'B and back to ground. 1'0 If there is no personal response from the subscrib'ers set, the operator closes the contacts at [2 thus operating the" relay" 5|. The operator the'n actuates the dial interrupter H" winch may be of any suitable type, at the code numlte'r' is given by the subscriber. The resultin Gilfflififi pulses are carried through the line wire 42' to the relay 52'. This relay is" thus energized the predetermined number of times. At each poise from H a pulse of current fiows' from the battery 20 3! through the operating magnet 53' of the rotary selector 43. The selector 43 having beenset to closethe circuit at, for example, thefourth pulse will then bridge the resistance 85 across the line wires 4] and 42. ll his resistance is designed to 5" produce the same effect on the line circuit as though the latter were closed through the subscribers setB by someone lifting. the receiver from the hook and thusthe operator receives a characteristic response by use of the code'nuin- 0 her on th'eiht'errupter I]. This response is take'n as identifying. the person making. the original request which may then be complied" with.
The actuation of the relay 52alsopermits current from the battery 32 to fiow through the 5 solenoid 54 and lift the plunger 55' breaking the contact at l3 and-lifting the dasher of the dash-- pct 56. The dash pot and the successive pulses of current keep the contactat l3 broken untilafter the predetermined number oi pulses 40 operated the selector 43 and sufficient time has elapsecltoallow the operatorto note the bridging of the-line wires- 4-] and {12 by the resistance When the pulsescease, the stem 55 sinks gradu ally into the dash pot until the contact at 13 45 at B. He calls the operator at A in the usual manner and states his desire and gives his secret code number, in this case the number four. The operator closes the contact at I0 and waits for a response and an authorization to make the charge from B. Receiving no answer, the operator opens the contact at I0 and closes that at I2 and operates the interrupter II to send four pulses. The above described process takes place and the operator receives the same signal from the line as though the receiver at B had been lifted. This response to the code number is taken as authority to make the charge.
The above embodiment and description are applied to the case of a single party private line. Fig. 2 illustrates another embodiment of the invention as applied to a four party line with the customary selective ringing installation. The customary apparatus for one of the four subscribers is indicated generally by the letter K from which the party line wires MI and I42 lead to a central station jack indicated generally by the number I20. The usual A. C. ringing generator I3I working through the biasing batteries I33 and I34 supplies combined alternating and direct current to the wires I44 and I45 and thence through apparatus to be described to the jack I20 and so to the line wires MI and I42.
The usual operators set connected to the jack I20 is generally indicated at 0.
Assuming that subscriber has the party letter K and the secret code signal GDP and that he is at a public telephone away from home and has asked the operator to make a pay call elsewhere for him and has given the operator his home number to which to charge the pay call and his code signal by which to identify himself, the operator will call the subscribers private home telephone to receive confirmatory authority to make the charge. If no reply is received,
' the operator closes the contacts II2 closing a circuit from the battery I 38 to actuate the relays I5I and I50. Alternating current from the generator I3I and direct current from the battery I34 then flow through the wire I45 and the lower contacts of relay I5I. The alternating current passes thence via condensers I9I and I93, lower contacts of relay I 50, jack I20, line wire I4I, condenser I94, relay winding I 55, line wire I42, tip side of jack I20, upper contacts of relay I50, condensers I92 and I90, and upper contacts of relay I5I to ground. This current operates relay I closing a circuit for the direct current. The direct current passes from the lower contacts of relay I5I through inductive -resistance I8I, relay windings I61, I68, I69, and
I10, lower contacts of relay I50, jack I20, line wire I4I, button switch II6, contacts of relay I55 (closed now by the alternating current), and winding of relay I59 to ground. This current operates relay I59 and tends to operate polarized relays I61 and I68 but not polarized relays I69 and I10. This actuation of relay I59 allows current from battery I35 to pass via relay I59, line I42, jack I20, upper contacts of relay I50, windings of relays I63, I64, I and I66, inductive resistance I80, and upper contacts of relay I5I to ground, thus tending to actuate polarized relays I63 and I64 but not polarized relays I65 and I66. Battery I32 is connected at one side to ground and at its other side to the leads of the windings of the two sets of relays I63, I64, I65, I66 and I61, I68, I69, I10. Batteries I34 and I32 and windings I61, I68, and I59 are so balanced against each other that in the case now being considered the combined effect of the two batteries is surficient to operate relay I68 but not relay I61. Also batteries I34, I32, and I35, resistance I82, and windings of relays I63 and I64 are so chosen that their combined efiect will operate both relays I53 and I64. Closing of relays I63, I64, and I68 closes a three branched circuit from battery I31, through lamps D, C, and F in parallel, and the contacts of relays I63, I64, and I68 in parallel to ground, thus lighting lamps CDF and confirming the code identification given by the subscriber.
The alternating current first traced out above will also pass via the windings of relays I56, I51 and I58 as well as relay I55 from line wire I4I to line wire I42 and will operate these relays, but relay I60 is polarized against direct current from line wire I 4| and so will not operate, while the windings of relays I6I and I 62 are connected to line wire I 42 and together with relays I59 and I60 are wound not to be operated by battery I32 alone. Hence in the instant case only relay I59 of this group will be actuated and only subscribers set K to which relay I59 is assumed to belong will respond with its characteristic identificatory signal.
The button switches H6, H1, H8, and H9 are included merely for convenience to enable the subscriber to dispense with this service if he so wishes.
In analogous fashion the operation of key II2, I I3 or II4 will bring a unique response from the bank of signa1 lamps in each case.
A code sign and its corresponding signal may be changed for any one subscriber by changing the resistance I82, I83, I84 or I85 as the case may be, by adding or removing a battery I35 or I36, by changing the relay I59, I60, I6I or I62 respectively, by inverting the connections to the line wires MI and I 42, etc. In particular, Fig. 3 illustrates twenty-four difierent arrangements of the signal circuit closing relay with resistances of only two difierent sizes available and with or without a battery. Thus a great variety of possible code signals is available for assignment to any one subscriber.
Although the invention as herein shown is illustrated as combined for use with a hand operated central station, it may obviously also be combined with the supervising operators position of an automatically operating central station since in no case is the construction or mode of operation of the central station involved. Furthermore, the invention is not limited to application to telephone systems but by suitable modification in detail may be applied to any communication systems in which messages are transmit ted electrically between two or more stations.
The embodiments of the invention herein disclosed are obviously merely illustrative and may be modified and departed from in many ways without departing from the spirit and scope of the invention as pointed out in and limited only by the appended claims.
What is claimed is:
1. In a communications system, a first station, a second station, electrical means to transmit a call signal from the first station to the second station, and electrical means for transmitting messages therebetween, in combination with means at the first station to transmit a predetermined signal distinct from the call signal to the second station, and means at the second station responsive only when the second station is idle to the predetermined signal to return to the first station a predetermined signal.
2. In a communications system, a first station, a plurality of second stations, electrical means to transmit a call signal from the first station to any second station, and electrical means for transmitting messages therebetween, in combination with means at the first station to transmit a predetermined signal to any one of the second stations different from the call signal of that second station, and means at the particular second station responsive only when the second station is idle to the predetermined signal to return to the first station a predetermined signal.
3. In a communications system, a first station, a plurality of second stations, and electrical means for transmitting messages therebetween, in combination with means at the first station to transmit to the second stations any one of a set of predetermined signals each uniquely pertaining to one second station, means at each second station responsive only to the signal pertalning to that station to return to the first station a predetermined signal characteristic of the said particular second station, and means at the first station consisting of a plurality of lamps, operable by each predetermined return signal, to show a code characteristic of the said particular second station.
4. In a telephone system, a central station, a subscribers station, electrical means at the central station to transmit a call signal to the subscribers station, and electrical means for transmitting messages therebetween, in combination with means at the central station to transmit a predetermined signal different from the call signal to the subscribers station, and means at the subscribers station responsive only when the subscribers station is idle to the predetermined signal to return to the central station a predetermined signal.
5. In a telephone system, a central station, a plurality of subscribers stations, electrical means to transmit a call signal from the central station to anyone of the subscribers stations, and electrical means for transmitting messages therebetween, in combination with means at the central station to transmit a predetermined signal different from the call signal to any one of the subscriber's stations, and means at the particular subscribers station responsive only when the particular subscribers station is idle to the predetermined signal to return to the central station a predetermined signal.
6. In a telephone system, a central station, a
plurality of subscribers stations electrically connected thereto, and electrical means for transmitting messages therebetween, in combination with means at the central station to send simultaneously to several of the subscribers stations any one of a variety of electrical signals each of predetermined electrical characteristics, means at each of several of the subscribers stations responsive to and actuable by one and only one such signal to automatically return to the central station a responsive signal characteristically identifactory of the responsive subscribers station, and means at the central station consisting of a plurality of lamps, operable by each predetermined return signal, to show a code characteristic of the responsive subscribers station, no two subscribers stations being capable of responding simultaneously to the same such signal from the central station.
7. In a telephone system, a central station, a subscribers station, and an electrical circuit connecting the same, in combination with means at the central station to send to the subscribers station an electrical signal of predetermined sign and character and comprising a direct current component and an alternating current component, means at the subscribers station responsive to and actuable only by the electrical signal of predetermined sign and character to return to the central oflice a responsive electrical signal of predetermined sign and character, and. further means at the central station actuable only by the responsive signal to identify the subscribers station responding.
8. In a telephone system, a central office and a plurality of subscribers stations electrically connected thereto, in combination with means at the central station to send simultaneously to a group of the subscribers stations any one of a variety of electrical signals each of predetermined sign and character and comprising a direct current component and an alternating current component, means at each of several of the group of subscribers stations responsive to and actuable by one and only one of the variety of electrical signals to return to the central station a responsive electrical signal characteristic and identificatory of the responding subscribers station, and further means at the central station actuable by the responsive signal to give an indication identifying the responding station, no two subscribers stations in any one group having means responsive to the same signal.
HOWARD T. JEANDRON. ADELBERT R. MORTON.
US659032A 1933-03-01 1933-03-01 Communication system Expired - Lifetime US2045146A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US659032A US2045146A (en) 1933-03-01 1933-03-01 Communication system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US659032A US2045146A (en) 1933-03-01 1933-03-01 Communication system

Publications (1)

Publication Number Publication Date
US2045146A true US2045146A (en) 1936-06-23

Family

ID=24643755

Family Applications (1)

Application Number Title Priority Date Filing Date
US659032A Expired - Lifetime US2045146A (en) 1933-03-01 1933-03-01 Communication system

Country Status (1)

Country Link
US (1) US2045146A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3904830A (en) * 1972-07-03 1975-09-09 Mek Tronix Lab Call tracing and identification system
US3997732A (en) * 1972-07-03 1976-12-14 Mek-Tronix Laboratories Corporation Call tracing and identification system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3904830A (en) * 1972-07-03 1975-09-09 Mek Tronix Lab Call tracing and identification system
US3997732A (en) * 1972-07-03 1976-12-14 Mek-Tronix Laboratories Corporation Call tracing and identification system

Similar Documents

Publication Publication Date Title
US2183649A (en) Automatic telephone system
US2045146A (en) Communication system
US1831385A (en) Telephone system
US2583783A (en) Pay station circuits for automatic telephone systems
US2172579A (en) Key sender
US3259697A (en) Telephone signaling system
US2301837A (en) Testing arrangement for trunks to community dial offices
US2370239A (en) Special service telephone system
US2332872A (en) Station circuit
US2064186A (en) Intercommunicating system
US2153574A (en) Automatic switching system and apparatus
US2042532A (en) Remote signaling system
US2105898A (en) Telephone exchange system
US1218563A (en) Signaling system.
US1904252A (en) Telephone system
US1919317A (en) Telephone system
US2065894A (en) Telephone system
US2222099A (en) Telephone system
US1859476A (en) Semiautomatic telephone system
US2093080A (en) Teletypewriter system
US1592646A (en) Automatic telephone system
US2352271A (en) Teletypewriter pay station circuit
US1284924A (en) Automatic party-line telephone system.
US1312702A (en) martin
US1830873A (en) Telephone system