Patent GB-785755-A (GB)
Title: Improvements in or relating to electric telegraph equipment
Inventor: GAITE HAROLD DODIMEAD
IPC: H04L5/22
Filed: 1954-06-04
Abstract: 785,755. Telegraph transmitters. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. MAY 13, 1955 [June 4, 1954], No. 16563/54. Class 40 (3). In electric telegraph equipment, in which automatic transmission from a plurality of tape readers is effected, the different readers are operatively connected up over the wipers of an electromagnetically - operated step - by - step switch which is automatically advanced through positions in which no tape readers are connected, but in which control of transmission is effected. The positions not connected to the tape readers may be used to transmit information, such as the call sign or the message number or a test signal. The step-by-step switch of known type, shown in Fig. 1 (Prov.), comprises a magnet 13 operating an arm 14 carrying a pawl 15 engaging a ratchet 16 on a shaft carrying three arms 17 disposed at 120 degrees and provided with six wipers engaging twelve sequential columns with contacts 18 arranged in six levels. The wipers of the arms are connected by a slip-ring arrangement and are connected through a plug PLV and socket SKV to a distributer, preferably electronic, and as described in Specification 765,227, in which potentials selectively and simultaneously applied to a number of input leads are passed in time sequence to an output line. When transmission is to be effected the tape readers Y, Z are plugged into double sockets SKYA, SKYB and SKZA, SKZB connected to positions 11, 12 of the uniselector and tape contacts TSY are closed so that a circuit is completed for relays A/4 and F/4, the latter being slow to operate. The wipers are normally in position 2 in which the wiper F, Fig. 3, completes a circuit for a magnet N, stepping the coder controlling the transmission of the serial number of the message, which is not operated and does not allow capacitors C1, C2, C3 to charge to any appreciable extent. At contact A2 relay A/4 locks up and at contacts A3, A4 the short circuit of tight-tape contacts TTY is removed and a circuit is prepared for the magnet Y<SP>1</SP> of the Y tape reader. Earth applied to contact V7 operates the distributer which applies a pulse to terminal V12 operating the stepping magnet to move the wipers to position 3 in which letter shift is again transmitted. The wipers are moved to positions 4, 5 in which earth applied to terminal V11 holds the output at mark and the wipers pass to position 6 in which a relay H/1 is operated so that over contact H1, the pulses at V12 from the distributer operate a magnet P to step the call-sign coder connected at socket SKP until the end of its operation, denoted by the figure-shift signal, causes contacts PA to move to the right to break the circuit of relay H/1, but to prepare an alternative circuit for its operation in position 10 to complete the transmission of the call-sign. When relay H/1 falls off, the next pulses applied at V12 step the uniselector over positions 7, 8, 9 on which the number of the message is transmitted, and connected via socket SKN to the number coder, and on reaching position 10 the remainder of the call-sign is transmitted. When the wipers reach position 11, a relay E/3 is operated and at contact E3 the circuit to the stepping magnet U is broken and subsequent pulses at V12 pass to magnet Y<SP>1</SP> to step the tape reader Y to transmit its message at the end of which contacts TSY open to release relay A/4, but an alternative circuit is completed for relay F/4 at position 11 over released contact A1, and rectifier MR1. The next pulse steps the uniselector to position 12 which still holds relay F/4 and the next pulse at V12 advances the selector to position 1 in which relay F/4 is held by a circuit over the back contact J1. When the selector is stepped to position 2, relay F/4 is no longer energized and the distributer ceases operation. The capacitors C1, C2, C3 are able to discharge and operate magnet N which steps the serial number coder to add one to the number next to be transmitted. If there is a tape in the Z reader, contacts TSZ will be closed, and relay B/4 will operate and control the same sequence of operations. If it is desired to send a message without a serial number switch SWA is operated. At contacts SWA1 the circuit is maintained through magnet N and capacitors C1, C2, C3 are prevented from charging, and at contacts SWA2 earth is applied in positions 7, 8, 9 to terminal V11 to hold the output line in the marking condition. To send a test message, key SWB is operated and relays J/4, F/4 are operated, so that the distributer is set into operation and completes its cycle independently of the operation of the switch, and comes to rest in position 1 and the test message is sent out under control of the test coder plugged into socket SKT. When it is desired to stop sending the test message, key SWB is restored and contacts TA, which open at the end of the message, allow relay J/4 to release and the uniselector steps to position 2 in which relay F/4 releases and the operation ceases. If short messages under control of a routine coder are to be transmitted, a switch SWC is momentarily operated causing the operation of relays D/4, J/4 which at contact D4 closes the circuit of magnet Q of the routine coder which is plugged into socket SKQ, Fig. 2. As relay E/4 is operated, contacts QA which are closed at beginning of operation of the coder maintain the circuit of relay D/4, and when the message has been transmitted the contacts QA are opened and relays D, J, E, F are released so that the selector is stepped to position 2. Transmission may be interrupted by operating key SWD which at contact SWD2 removes earth from terminal V7 stopping the distributer and providing a locking circuit for relay B/4 if operated. If relay A/4 had been operated its locking circuit is maintained over contacts SWD1 of the switch, and sending in either case is resumed when the switch SWD is restored to normal. The connection of positive potential from terminal V10 to V9 by the operation of switch SWE operates the distributer to apply a continuous spacing signal to the line, and the operation of the switch SWF allows the call sign and message number to be transmitted when a message is sent from a common transmitter to several channels simultaneously. If a keyboard transmitter is to be brought into use, the switch MA, Fig. 4, is operated and a circuit is completed over contacts D3, switch MA relay G/4, contact F3, relays J/4 and F/4. At G3 a circuit is prepared for applying pulses to V7 and G4 connects the key-release magnet, which is connected between points M5 and M14, to the distributer. The relays J/4, E/4 are held energized until relay E/3 is operated, when the selector reaches the position 1. Negative potential connected from the distributer to the terminal V15 charges capacitor CM and the contacts MB, changed over on each key operation, apply a negative pulse to terminal V7 for a predetermined time. Various interlocking arrangements are provided to prevent more than one piece of equipment controlling transmission at any particular time. The gas tube LP2 is operated on each pulse applied to V12, and the opening of the tight-tape contacts TTY or TTZ removes earth from the terminal V7 and arrest the operation of the distributer. Specifications 697,913, [Group XXXVII], and 747,188 also are referred to.