Patent GB-659733-A (GB)
Title: Improvements in or relating to telegraph systems
Inventor: DAIN GORDON TAYLOR
IPC: H04L12/00
Filed: 1947-01-10
Abstract: 659,733. Telegraph transmitting-systems. BRITISH TELECOMMUNICATIONS RESEARCH, Ltd. Jan. 10, 1947, No. 955. [Class 40 (iii)] A telegraph transmitting arrangement includes an arrangement for discriminating between signals in accordance with the constituent elements of the signal and to cause a switching operation to take place in response to the predetermined repetition of a particular message character signal or to a combination of message character signals. In one arrangement the circuit is arranged to respond to a predetermined repetition of a signal or signal combination to effect one switching operation and to respond to a predetermined repetition for a different number of times to effect a different switching operation. The arrangement may be used to control an automatic transmitter to transmit a message serial number and subsequently to connect automatically a message transmitter to the line. At the end of the message the line is switched back to the automatic number transmitter. On the closure of a key KP associated with a transmitter MAH1, a circuit is completed for a relay P which'locks up over contact P1 and at contact P2 closes a circuit for a relay A. At contact P4 a circuit is closed for a relay B which operates less quickly than relay A and at contact B2 changes over the locking circuit of relay P. At contact A2 a circuit for the magnet CM1 of the transmitter MAH1 is interrupted and at contact Al, a relay BA is released allowing contact BA2 to close, thereby operating relay BB which at contact BB2 completes a circuit for the magnet CM3 of an automatic transmitter for transmitting a serial number over contact T3 connected to the line L. The line impulses are applied to a relay M which at contact M1 repeats the impulses to a circuit comprising a condenser C1 and a discharge tube NT1 in series with a relay D. The capacity of the condenser C1 is chosen in connection with the resistances R1, R2 and the striking voltage of the tube NT1 so that one or more letter-shift signals which are arranged to have solely a positive start impulse are not sufficient to cause the tube to strike. All other character signals operate relay D which at contact D1 effects the discharge of a condenser C2 in a charging circuit comprising resistances R4 and R3 when contact BA3 is open. The voltage at the condenser C2 is applied to a second discharge tube NT2 in series with a relay E. After the transmission of a message number from the transmitter ANH, a series of five letter-shift signals are transmitted and since relay D is not operated, contact D1 is not closed and condenser C2 charges to a value such that the tube NT2 strikes and relay E operates closing a locking circuit over contacts E1, F1 (unoperated) and also an operating circuit for relay F which operates, locks itself over contacts G1 (unoperated), F3, and at F1 opens the locking circuit of the relay E. At contact F4, relay A is released, so that relay BA energizes and relay BB releases allowing the completion of the circuit of magnet CM1 of the transmitter MAH1. At the end of a message transmission, ten letter-shift signals are transmitted. Over a circuit comprising resistances R3, R4 in series condenser C2 is again charged so that relay E operates again and locks up over contacts E1, BB1 (unoperated) and F1 (operated). A circuit is completed for a relay G which opens the locking circuit of relay F which slowly releases and opens the locking circuits of relays. E, G. If, in the meantime, key KQ of the transmitter MAH2 has been actuated, relay Q will have operated, relay A will operate and the transmission of a serial number from ANH followed by the message from MAH2 will take place. The arrangement by which the switching from the automatic numbering device to the message transmitter is effected by five letter-shift signals and from the message trans: mitter to the automatic numbering device is achieved by ten letter-shift signals is desirable in cases in which a message is received and retransmitted by an intermediate station and the message number from the originating station is preceded by a further serial number. The numbering transmitter may be switched out of operation by a key KN, operating a relay X which locks over contact X1 and at X2 interrupts the circuit of the magnet CM3 and a key KH may be operated to interrupt the transmission of a message. In a modification, Fig. 8 (not shown), two impulse relays replace the single relay M of Fig. 6, the marking and spacing contacts being connected to two circuits each comprising a condenser, discharge tube and a relay, one circuit being arranged to fire when a signal comprises two successive marking elements, whilst the other circuit is fired by spacing current of duration greater than one, but less than two successive elemental periods. With such an arrangement, certain characters, viz. F, J, Y do not fire either circuit, and if the contacts of the discharge tube relays are connected in parallel, the condenser C2 will not be discharged during the transmission of these characters either singly, repeatedly or in any combination. The main arrangement may be such that, following a letter-shift signal, the tube NT1 is not fired until two other characters have been transmitted. The Provisional Specification describes modified timing-circuit arrangements.