US2296353A - Signal system - Google Patents

Description

Sept. 22, 1942- a. J. KlNssuR SIGNAL SYSTEM Filed Oct. 19, 1940 nv VENTOR By B. J. K/NSBURG A T'mpuE- Patented Sept. 22, 1942 e I, r

SIGNAL SYSTEM Boris J. Kinsburg, Riverdale, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application October 19, 1940, Serial No. 361,879

Claims.

This invention relates to signal systems and particularly to signal systems having dynamic regulators governed by pilot current.

One object of the invention is to provide a signal system having regulators under control of pilot current that shall prevent exaggerated transient transmission irregularities,

Another object of the invention is to provide a signal transmission line having dynamic regulators under control of pilot current for governing the strength of the transmitted signals that shall divide the line into sections in a manner to permit the free transmission of signal currents from one section to another section and to control the pilot current in a section according to the integrated variations of the pilot current in a preceding section while preventing the transmission of transient exaggerated irregularities from one section to another section.

A further object of the invention is to provide a signal transmission line of the above-indicated character that shall divide the line into sections by blocking the transmission of pilot current from one section to another section while permitting the free transmission of signal currents from one section to another section and that shall reintroduce constant amplitude pilot current in a subsequent line section which is controlled according to the integrated variations of the pilot current in the preceding line section.

In long signal transmission lines provided with dynamic regulators governed by pilot current for controlling the strength of the line signals, trouble is at times experienced by reason of exaggerated transient transmission irregularities. If there is a change in the strengths of the signal and pilot currents, the pilot current governs the dynamic regulators to correct for the change in the strength of the signals. A number of the regulators make correction for the change in the signal strength with the result that an overcompensation is effected for the change in signal strength. Then during a period of time the pilot current operates the regulators to efiect an oscillatory movement of the signal strength'above and below normal value until a steady normal state is reached. The longer the transmission line is in length, the greater will be the transient swings in the signal strength.

The present invention provides means for limiting the transient transmission irregularities on a signal transmission line provided with dynamic regulators, The transmission line is divided into sections with blocking means to prevent the transmission of the transient irregularities from one section to another section while permitting the free transmission of signal currents from one section to another section.

In one form of the invention a blocking filter is inserted in the signal transmission line with dynamic regulators placed on each side of the blocking filter. The blocking filter permits the free transmission of signal currents therethrough while preventing the transmission of the pilot current which controls the 'dyamic regulators. A source of constant level pilot current is connected tov the line section beyond the blocking filter. The pilot current from this source is controlled in accordance with the integrated variations of the pilot current on the line section before the blocking filter. A resistance element having a negative temperature coefiicient of resistance is inserted in the circuit between the source of pilot current and the line section beyond the blocking filter. This resistance element is controlled by a heater coil which, in turn, is governed by the pilot current on the line section before the blocking filter.

A filter which selects the pilot frequency is connected to the line section before the blocking filter. The output from the pilot filter is amplified and then rectified. The rectified current is amplified and supplied to the heater coil for controlling the resistance element in the pilot current circuit connected to the line section beyond the blockin filter. In the above manner the variations in the pilot current on the line section before the blocking filter are integrated for controlling the pilot current impressed on the line section beyond the blocking filter. The transient transmission irregularities in the line section before the blocking filter are not transmitted to the line section beyond the blocking filter. However, the integrated value of the'pilot current variations on the line section before the filter is employed to control the pilot current on the line section beyond the filter.

In the accompanying drawing:

Fig. 1 is a diagrammatic View of a signal system constructed in accordance with the invention; and

Fig. 2 is a modification of the signal system shown in Fig. 1.

Referring to Fig. 1 of the drawing, a transmission line comprising conductors l and 2 is provided with a number of amplifiers four of which, 3, 4, 5 and 6, are shown. The amplifiers 3, 4, 5 and 6 may be of any suitable type and are controlled by regulators T, 8, 9 and Ill. The regulators may be of the type disclosed in the patent to R, R. Blair 2,179,915, November 14, 1939. The regulators are of the dynamic type and eifect a quick response in correcting any change in the signal strength. Carrier current signals are carried by the line comprising conductors I and 2 and a pilot current supplied by a source II is provided for controlling the operation of the regulators.

A signal transmission line constructed as above indicated and provided with dynamic regulators for controlling the amplifiers is liable to be subjected to exaggerated transient irregularities. If there is a change in the signal strength, the pilot curent will operate each of the regulators for correcting the signal currents. Inasmuch as a number of regulators attempt to make the corrections, it is apparent that overcompensation will be effected. The signal strength will be carried above and below normal value for a period of time. These transient irregularities will increase according to the length of the line and the number of amplifiers thereon.

In order to limit the transient irregularities which may be transmitted along the conductors I and 2, the line is divided in sections by means of a pilot blocking filter I2. The filter I2 blocks the transmission of pilot current and permits the free transmission of the signal currents. A new pilot current which may have the same frequency as the source II or a different frequency is supplied from a source I3 to the line section beyond the blocking filter I2. The circuit be-. tween the source I3 and a line section beyond the filter I2 includes apilot filter I4 and a resistance element I5. The resistance element negative temperature coefficient. of resistanceand may, for example, be composed of silver sulphide. The resistance element I5 is controlled by a heater coil I6 to govern the strength of the pilot current supplied from the source I3 according to the integrated variations of the pilot current on the. line section before the filter I2.

A control circuit I1 which is connected to the line. section before the filter I2 is provided for controlling the heater coil IS. The circuit II comprises a pilot filter I8, an amplifier tube I9, a two-element rectifier tube and a direct current amplifier tube 2!. The pilot filter I8 is directly connected to the line section before the filter I2. The output circuit from the filter I8 is connected to the input. circuit of the amplifier I9. Plate potential for the amplifier tube I9 and also for the amplifier tube 2I is supplied by a battery 22. The alternating current output. circuit of the tube I9 comprises a tuned circuit 23 and a condenser 24. The rectifier tube 29 is coupled to the output circuit of the tube I9 by means of a condenser 25 and a resistance element 26. The rectifier circuit of the tube 20 includes the resistance element 26 and resistance .2

element 21. The potential drop across the resistance element 21 is impressed on the grid of the direct current amplifier 2I. The output circuit of the direct current amplifier 2i includes a resistance element 28, the potential drop across which is impressed on the heating coil I5.

In a signal system constructed as above indicated signal currents may be freely transmitted from one end of the line to the other whereas pilot current from the source I I cannot be transmitted beyond the pilot blocking filter I2. Accordingly, any transient swings produced on the line section before the blocking filter I2 cannot be transmitted to. the line section beyond the I5 has a .n

blocking filter. It is necessary, however, to con reference characters.

trol the pilot current from the source I3 accord-' ing to the integrated value of the pilot current on the line before the blocking filter I2. Control of the pilot current from the source I3 according to the integrated value of the pilot current before the blocking filter is effected by means of the control circuit I'I. Although only one blocking filter is shown in Fig. l of the drawing, it is to be understood that any number of blocking filters may be employed to divide the line into any desired number of sections.

The system shown in Fig. 2 of the drawing is a modification of the system shown in Fig. 1 and like parts have been indicated by similar The line shown in Fig. 2 is divided into sections by a pilot blocking filter the same as the line shown in Fig. 1. Moreover, a control circuit I! which is similar to the control circuit I'I shown in Fig. l is provided for controlling a heater coil It. A circuit 38 comprising an overloaded amplifier tube BI and a pilot filter 32 is provided for supplying pilot current to the line section beyond the blocking filter I2. The input circuit of the amplifier tube 3i is connected across the output circuit of the amplifier tube I9. The overloaded amplifier tube BI is thus supplied with amplified pilot current from the line section before the blocking filter I2. The output current from the amplifier tube 3| has a substantially constant amplitude and is supplied through a transformer 33, the pilot filter 32 and a resistance element 34 to the line section beyond the blocking filter I2. The resistance element 34 has a negative temperature coefficient of resistance and is similar to the resistance element I5 shown in Fig. 1 of the drawing. The resistance element 34 is controlled by control circuit I'I according to the integrated pilot variations on the line section before the blocking filter I2.

Modifications in the systems and in the arrangement and location of parts may be made within the spirit and scope of the invention and such modifications are intended to be covered by the appended claims.

What is claimed is:

1. In a signal system a signal transmission line, blocking means on the line dividing it into sections, means supplying pilot current to said sections on each side of the blocking means, said blocking means preventing the transfer of pilot current therethrough while permitting the free transfer of signals therethrough, amplifiers in respective sections each including a regulator controlled by the pilot current in its section and attaining a state of stable operation within a limited period of time after a change occurs in pilot current strength, and means for controlling the pilot current beyond said blocking means according to the integrated variations of the pilot current before the blocking means integrated over a period of time greater than said limited period required for said regulator to attain a state of stable operation.

2. In a signal system, a transmission line, blocking means dividing the line into sections, dynamic regulators on each side of said blocking means, means impressing pilot current on the line on each side of said blocking means for controlling the dynamic regulators, said blocking means preventing the transfer of pilot current therethrough while permitting the free transfer of signals therethrough and said dynamic regulators attaining a state of stable operation Within a limited period of time after a change occurs in said pilot current strength, and means for con trolling the pilot current beyond said blocking means according to the integrated variations of the pilot current before the blocking means integrated over a period of time greater than said limited period required for said regulators to attain a state of stable operation.

3. In a signal system, a transmission linehaving a plurality of dynamic regulators thereon controlled according to the strength of pilot current, said dynamic regulators attaining a state of stable operation within a limited period after a change occurs in the strength of said pilot current, blocking means on said line for the pilot current frequency dividing the transmission line, means for reintroducing pilot current in the line beyond said blocking means, and means for controlling said reintroduced pilot current according to the average of the fluctuations in the pilot current before said blocking means averaged over a period approximately equal to that required by said regulators to attain a state of stable operation after the occurrence of a change in the strength of the controlling pilot current.

4. In a signal system, a transmission line carrying signal currents and pilot current, blocking means on said line for the pilot current frequency, dynamic regulators for said line on each side of said blocking means, means for impressing pilot current on the line beyond said blocking means, said dynamic regulators being controlled by the strength of the pilot current in the respective portions of the line and attaining a state of stable operation Within a limited period after a change occurs in said pilot current strength, and means controlled by pilot current on the line before said blocking means for governing the pilot current introduced in the line beyond the blocking means in accordance with the integrated value of the pilot current variations before the blocking means integrated over a period approximately equal to that required by the regulators to attain a state of stable operation after the occurrence of a change in the strength of the pilot current 5. In a signal system, a signal transmission line, a blocking filter dividing the line into sections, dynamic regulators on each side of said filter, means impressing pilot current on each side of said filter for controlling the dynamic regulators, said blocking means preventing the transfer of pilot current therethrough while permitting the free transfer of signals therethrough and said dynamic regulators attaining a state of stable operation within a limited period after a change occurs in the strength of said pilot current strength, a circuit for supplying pilot current to the line beyond said filter, resistance means in said circuit for governing the pilot current, and means for controlling said resistance means according to integrated variations of the pilot current on the line before said filter integrated over a period of time approximately equal to that required by the regulators to attain a state of stable operation after the occurrence of a change in .the strength of the pilot current 6. In a signal system, a signal transmission line having signal currents and pilot current thereon, a blocking filter on said line permitting the free fiow of signal currents therethrough and blocking the passage of pilot current, dynamic regulators on each side of said filter for controlling the signal currents, a source of pilot current connected to the line beyond said filter, said dynamic regulators being controlled by the strength of the pilot current in the respective portions of the line and attaining a state of stable operation within a limited period after a change occurs in the strength of said pilot current, a resistance element having a negative temperature coefilcient of resistance for governing the pilot current from said source, and means controlled according to the integrated variations of the pilot current on the line before said filter integrated over a period of time approximately equal to that required by the regulators to attain a state of stable operation after the occurrence of a change in the strength of the pilot current for governing the temperature of said resistance element.

'7. In a signal system, a signal transmission line having signal currents and pilot current thereon, a blocking filter for dividing the line into sections, amplifiers including dynamic regulators on each side of said filter, said filter blocking the flow of pilot current and permitting the free flow of signal currents, a source of pilot current connected to the line beyond said filter, said dynamic regulators being controlled by the strength of the pilot current in the respective portions of the line and attaining a state of stable operation within a limited period after a change occurs in the strength of said pilot current, a resistance element having a negative temperature coeificient of resistance for governing the pilot current from said source, a heater element for controlling the temperature of said resistance element, a pilot filter for obtaining pilot current from the line before said blocking filter, and means for amplifying and rectifying said selected pilot current to,

control said heater and govern the pilot current beyond said blocking filter according to the integrated variations of the pilot current on .the line before the blocking filter integrated over a period of time approximately equal to that required by the regulators to attain a'state of stable operation after the occurrence of a change in the strength of the controlling pilot current.

8. In a signal system, a signal transmission line having signal currents and pilot current thereon, a blocking filter for dividing the line into sections, said filter blocking the fiow of pilot current and permitting the free flow of signal currents therethrough, dynamic regulators on the line on each side of said blocking filter under control of pilot current, a pilot filter connected to the line before said blocking filter for selecting the pilot frequency, means for controlling a portion of the output from the pilot filter .to obtain a constant output and for supplying this constant output pilot current to the line beyond the blocking filter, and means controlled by the integrated output from the pilot filter for governing the pilot current supplied to the line beyond the blocking filter.

9. In a signal system a signal transmission line having signal currents and pilot current thereon, a blocking filter for dividing the line into sections, said filter blocking the fiow of pilot current and permitting the free flow of signal currents therethrough, dynamic regulators on the line on each side of said blocking filter under control of pilot current, a pilot filter connected to the line before said blocking filter for selecting the pilot frequency current, control means comprising an overloaded amplifier operating on a portion of the pilot filter output for obtaining a constant pilot current and for supplying the constant pilot current to the line beyond the blocking filter, a resistance element having a negative temperature coefiicient of resistance inserted in the connection of the constant pilot current to the line, a heater coil for controlling said resistance element, and means controlled by the integrated output from the pilot filter for controlling said heater coil to govern the pilot current supplied to the line beyond said blocking filter.

10. In a Signaling system a signal transmission line, means to impress pilot current on said line, a plurality of amplifiers included in said line at separated points, dynamic regulators individual to said amplifiers for controlling the gain of said amplifiers in accordance with the strength of the pilot current at the said respective amplifiers, said regulators responding to changes in pilot current integrated over a limited period of time, and a slow-acting pilot regulator located at a point in said line between groups of said amplifiers for controlling the strength of the pilot current transmitted to the group of amplifiers toward the receiving end of said line in accordance with the strength of the pilot current incoming from the group of amplifiers toward the transmitting end of said line, said sloweacting regulator responding only to changes in pilot current integrated over a longer period of time than that over which changes in pilot current are integrated to efiect response in said individual dynamic regulators. BORIS J. KINSBURG.

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