Patent GB-573869-A (GB)
Title: Improvements in or relating to electric impulse receiving arrangements
IPC: H04Q3/42
Filed: 1942-12-15
Abstract: 573,869. Impulsing circuits. STANDARD TELEPHONES & CABLES, Ltd., HARTLEY, G. C., and REYNOLDS, W. J. Dec. 15, 1942, No. 17849. [Class 40 (i)] In a signalling system, the response of the impulse relay is made to persist for a minimum period by an auxiliary relay. In one arrangement each impulse breaks down a cold-cathode gas discharge tube T, the discharge persisting through the impulse relay C after the cessation of the received impulse until a condenser CA is connected to the anode by the relapse of a relay X which is released by C and has a second winding associated with a condenser to delay its relapse for 40 milliseconds. In the modified circuit shown in Fig. 2 in which tube T is replaced by a thermionic tube T1, the impulse relay A is energized initially and energizes the auxiliary relay X and falls in response to each impulse opening the grid circuit so that it is unable to operate again, however short the impulse, until the auxiliaryrelay X has fallen back. Both circuits also have a pause-timing relay Y which has a selfinterrupting circuit in the interdigital intervals. The invention is applied to the control of a number-indicator, e.g. of the kind described in Specification 538,723. First system, Fig. 1. Relay ED is normally energized and consequently the arrival of A.C. breaks down the tube T and energizes C which is followed by P, Y, S, SS. This releases ED and extinguishes the tube releasing C where upon impulse timing relay X and relay G pull up. The control electrode of the tube now has an 80-volt bias in opposition to the rectified signal current instead of a 40-volt bias assisting this current. With the circuit in this condition the tube remains unoperated until the incoming current is interrupted. It then breaks down and operates C which energizes magnet SRM and releases P and X. The discharge is then interrupted as described above, C falls, SRM steps and after a further delay, X pulls up again. Subsequent impulses operate in the same way. In the interdigital pauses, the reception of A.C. persists after the re-operation of X, and Y falls back after a delay imposed by an associated condenser and makes a new circuit for itself over which it operates after a further delay. While Y is back, ground is connected to wiper 3. If the position of the pause corresponds to the station designation, this is without effect. If not, W comes up and prevents any change of the number indicator. At the end of the station code, Z pulls up and locks and connects AX instead of SRM to the impulsing circuit and, provided W has not operated, releases F to restore the number indicator and light a calling lamp. Next the dummy digit O is dialled. The operation of AX by the first impulse energizes ZA which locks, the remaining impulses being without effect and merely providing a period for complete release of the number indicator. At the end of the digit, Y falls, energizing ZB which locks, and then comes up again. ZB energizes SRM and Y on re-operating releases it so that the switch takes a step to connect up the first number indicator element to which the next digit is repeated. The first impulse also steps SRM but the same number indicator element remains connected up. At the end of the digit, Y falls and re-operates and the switch steps on to associate the next element which is similarly controlled. When all the elements have been set, the tone current is kept on the line for a duration equal to that of the interdigital pause and then removed. C and AX pull up as before but this time F is operated to hold the number indicator after the relapse of ZB. Relay X is released as before but, since the tone signal is no longer on the line in opposition to the 80-volt bias, its relapse does not extinguish the tube T and C remains operated. X therefore remains deenergized, and G, S, SS, Z, AX, ZA and ZB fall. T is extinguished by the relapse of S, C and Y are released and the wipers are advanced to their home contacts owing to the re-operation of Y. In the home position, ED pulls up again and Y falls without effect and remains unoperated. When a new signal is received, if it is for the station in question, Z operates and releases F to restore the number indicator. Otherwise, W operates and F is held. Faulty operation. If an impulse in the station code is missed, SRM does not reach the terminal connected to Z and relay W is operated to prevent any control of the number indicator. A missed impulse in the message portion gives the effect of an extra digit so that SRM reaches its home contacts -prematurely. Consequently ED pulls up when AX responds at the end of impulsing while Z is still operated. This unlocks relay F and the indicator is restored to normal. An abnormal pause enables Y to release again after stepping the switch SRM on. A circuit is thus made for W which either prevents the release of F or ensures the release of the number indicator at the end of the sending operation. If a digit is missing, F fails to operate and the indicators are released when ZB is released. Message to all stations. If 11 impulses are sent without any pauses, Z is operated without any prior operation of W at all the stations. All the number indicators can then be set effectively. This can be used merely to cancel all existing displays by the release of F since the automatic operation of Y will send SRM home if no further control is exercised by the sending station. Modified system, Fig. 2. When the circuit is seized, anode relay A pulls up and subsequently relay A follows the interruptions in co-operation with relay X as described in the opening paragraph. A also energizes AX, which follows the impulses, and G which remains operated until the termination of impulsing. Y pulls up initially over a home contact of the switch and remains operated while the switch is being stepped by the impulses of the station code. In the interdigital pauses, however, Y falls back and then re-operates in a circuit over one of its own back contacts. If the station code received is not that of the station, W pulls up over wiper 4 and the switch is stopped. If the proper code is received, Z pulls up and locks. The first impulse of the dummy digit preceding the numerical code energizes H which cancels the existing display and locks up. At the end of the digit, Y gives an impulse to SRM over wiper 4 and the switch takes a step so that the next digit is sent to the first number-indication element and relay H is released. During the numerical code, the switch is given a step by the first impulse of each digit over wiper 3 and a second step by relay Y over wiper 4 at the end of each digit. At the end of the last digit, the signal current is out off after a pause long enough to allow Y to release and re-operate to step the switch to its last contacts. A, AX are then released by the removal of the signalling currents and G falls to release Y and step the switch to its home terminals. R is operated on the last terminal and released when the switch moves. If the switch stops prematurely because the station code is not the proper one, the relapse of G when the message ends allows Y to operate in its self-interrupting circuit and step the switch to its home position relay H remaining locked over various circuits. The switch is similarly stopped by relay W if an elongated interdigital pause (caused by the suppression of an impulse) occurs in the message. If the message appears to contain an extra digit, the wiper reaches terminal 24 during impulsing and relay R operates. At the end of the impulsing, Y falls and H cancels the message on the indicator and remains held when the wipers reach their home position.