Patent GB-657071-A (GB)
Title: Improvements in or relating to electronic regenerative repeaters for start-stop telegraph systems
Inventor: WHEELER LEONARD KEITH
IPC: H04L25/04
Filed: 1948-10-15
Abstract: 657,071. Code telegraphy. POSTMASTER GENERAL. Oct. 15, 1948, No. 26882. [Class 40 (iii)] In an electronic regenerative telegraph repeater in which the incoming signals are applied to a receiving circuit controlling an outgoing relay through an electronic switching circuit, and in which a multi-vibrator circuit is arranged to apply to the receiving circuit conditioning impulses timed in relation to the speed of transmission of the signal elements, the multivibrator is under control of a timing circuit which is controlled by a start delay circuit which prevents the operation of the timing circuit until a start signal has persisted for a predetermined minimum period. The incoming impulses are applied over a line A to the suppressor grid of a valve V3 in a circuit SEC to the grid of which conditioning impulses occurring at the middle of the signal element are applied over conductor J from a multi-vibrator circuit MVB. When a negative (marking) impulse is applied over the line A, the conditioning pulse produces a negative pulse at the connection L to the screen grid of the valve V3. When a positive (spacing) impulse is received over the line A, negative pulses are derived at connections K, L, the pulses at K being slightly longer than those at L. A voltage N derived from a stopsignal circuit SSC, controlled by the timing control circuit MVC, varies between a high and low value, and during a stop signal period on the line the voltage N is at its higher value and when applied to the grid of the valve V1 of an Eccles Jordan circuit OTC, holds V1 conducting so that a re-transmitting relay OPR operates its contact to the marking position. During the transmission of a signal the voltage N is at the lower value and in response to a spacing signal the negative voltages applied at K, L to the suppressor grids of the valve V1, V2 hold both valves non-conducting until the longer pulse K allows the valve V2 to conduct and to operate relay OPR to send a spacing current to the outgoing line Y. The single negative pulse over the line L in response to a marking impulse holds the valve V2 non-conducting and the valve V1 conducting so that a mark is applied to the outgoing line Y. The multivibrator circuit MVB is controlled by a multivibrator control circuit MVC set into operation by a negative voltage D which is derived from a circuit SGSS, and which makes a valve V4 non-conducting so that a positive pulse is applied over connection G to the valve V7 making an associated valve V8 non-conducting and generating the positive pulses at J, the period of oscillation of the circuit MVB being adjusted to signal unit length, e.g. 20 milliseconds, by the condensers C4, C5 and resistances R9, R10. The operation of the circuit MVC causes a fall in voltage derived at E which renders the start delay circuit inoperative. The period of the circuit MVC is arranged to be that corresponding to six signal elements, e.g. 120 milliseconds, and a sixth pulse of a set of pulses H produced from the circuit SEC simultaneously with the pulses L effectively cuts off the valve V5 and restores the circuit MVC to the normal condition in which the valve V4 is conducting. When V5 becomes non-conducting, a positive impulse is applied over conductor I to the grid of valve V14 of stop signal circuit SSC so that a positive signal is applied over conductor N to the trigger circuit OTC to operate relay OPR to transmit a marking signal to the line Y. The generation of the negative voltage at D to operate the circuit MVC to bring the multivibrator circuit MVB into operation is effected by a start-gate and stop-signal suppressor circuit SGSS in conjunction with a start delay circuit SDC to which incoming signals are applied over sub-branches Q, P of a branch A1 of the incoming line X. When an incoming signal element is a space, the valve V9 conducts and reduces the potential at the anode output B which is applied to valve V11 of the signal delay circuit SDC to cut off valve V11 and render V12 conducting provided that neither of the voltages E, F derived from the circuits MVC and SSC is at its lower value. Should the space signal applied at the suppressor grid of the valve V12 persist for more than 10 milliseconds, the removal of the voltage which keeps the valve V11 cut off will take place, and V11 will conduct. A brief negative pulse will be applied from its screen grid circuit C comprising a capacitor C100 to the suppressor grid circuit of the valve V9 which ceases to conduct and biasses the valve V10 to conduction and the production of a negative impulse at the anode output D to operate the control circuit MVC for the multi-vibrator MVB. If the space signal does not persist for the period of 10 milliseconds, the valve V10 does not become conducting and the negative pulse at D is not generated. When a long spacing signal is received, the valve V9 is restored to its conducting condition after the short negative impulse has been transmitted at D and the valve V10 is held non-conducting. The time constant of the capacitor C10 and resistor R27 is arranged to be such that V10 will not conduct unless the space signal is greater than 110 milliseconds, but will conduct before the termination of a signal of 130 milliseconds, with the result that a negative pulse is sent over the conductor D to control the circuit MVC so that a positive pulse cannot be passed over the conductor I to the stop signal circuit SSC to control the circuit OTC to send a marking impulse to the line Y. This condition persists until the line condition reverts to marking when valve V10 is cut off and a positive pulse transmitted over connection D makes valve V4 of circuit MVC conducting so that a positive impulse is sent to the stop signal circuit SSC.