Patent GB-332687-A (GB)
Title: Electric signalling systems
IPC: H04B3/20
Filed: 1929-05-30
Abstract: 332,687. Standard Telephones & Cables, Ltd., (Assignees of Herman, J., Taylor, E. R., and Wright, S. B.). Feb. 5, 1929, [Convention date]. Manual exchange systems and apparatus; two-way repeating systems; inverting and transposing frequencies of telephone currents. - Relates to combined landwire and radio telephony and signalling systems, in which a two-wire terminal line is connected by a four-wire circuit to the transmitting and receiving aerials of a radio link: and c o m p r i s e s means for the alternative use of the system for the transmission of calls and technical information by means of type-printing telegraphy. The typeprinting impulses are transmitted bv tone-frequency apparatus connected at will to the twowire terminal line; and the printing receivers are maintained in continuous connection with the line from the receiving aerial. Figs. 1 and 2 show the circuits at a terminal station. The apparatus to the left of the chain line in Fig. 1 is situated in the exchange room TOR. whilst the apparatus and circuits to the right of the chain line join up with Fig. 2 and are situated in the technical or control room TCR. Two-way repeating system with echo-suppressing and secrecy devices. The two-wire line L' from the exchange room is connected through a balanced transformer 10 to the transmitting and receiving lines TL, RL. The transmitting channel TL includes amplifiers TA, TA<1>, a delay network TD, a second balanced transformer 11, secrecy device PM, and line TL<1> leading to the transmitting aerial. The receiving-channel comprises the line RL<1> from the receiving-aerial, the transformer 11, secrecy device PM, amplifiers RA<1>, RA, delay network DR, transformer 10 and twowine terminal L<1> to the exchange. During transmission of telephony, a rectifier TAD closes battery circuits through relays 12 - - 15, of which 12 and 13 serve to open short-circuits across the transmission channel, and relays 14, 15 disable the receiving-channel by opening switches and causing the divided transformers 16 - - 19 to assume a balanced non-transmitting condition. When transmission ceases, the relays 12 - - 15 are de-energized, the transmission channel is shorted, and the receiving-channel is in condition for reception. During telephone reception, a rectifier RAD energizes a relay 20 which opens the circuit from the rectifier TAD and removes its control of the channels. The line L<1> terminates in the exchange room in a jack J<1> which the operator may connect bv a cord circuit CC to any one of a number of telephone lines L, or to a line TCL for the transmission of type-printing signals. Type-printing apparatus and circuits. In the exchange room, two separate instruments are provided, one RP for reception only and the other TP a combined transmitter S and recorder R. Similar instruments TP<1> and RP<1> are also provided in the control room. The combined instruments TP and TP<1> are connected in series with a line TPL by which outgoing signal impulses are conveyed to a relay TR controlling a tonefrequency generator O. This is coupled at 30 to the transmitting line TCL. Outgoing messages are registered on the recorders R of both the combined instruments TP, TP<1>. Printer messages may be stored up and transmitted at suitable times by a tape sender TS. Received typeprinting signals do not pass through the repeater and line L<1>, but are shunted through a line RCL which includes an amplifier RCA and tone-filter RCF to a rectifier AD and a relay RR which controls the type-printers RP. RP<1> through a circuit RPL. A signal lamp 28 and a signal key RSK are provided in the exchange room and a signal lamp 29 in the control room for commnnication between the type-printing operators and the exchange operator. Operation. When the exchange operator desires to use the radio telephone channel for printer transmission, she operates the tone-key TK and throws her talking-key TMK to the right. Tonefrequency currents from the. source S are then sent out over the same path as voice currents, and on receipt of this signal the distant exchange operator connects up the printer sender. The home operator then plugs in to the jack TCJ. A battery circuit is thus closed through the wires TCL and L' and the relay PR, Fig. 2, and relays F, U, Fig. 1. The relay U energizes the supervisory lamp 27. The relay PR, which is balancedrelative to the transformer 10 by a dummy relay PN, closes three circuits-(1) through relay 21 to set the transmitting potentiometer at full gain, (2) through relay 22 to energize relays 12 - - 15 for opening the transmitting channel TL, TL<1> and closing the receiver channel RL, and (3) through relays 23, 24 to short the secrecy device PM. The receiver channel RL is not used for the reception of printer signals, which are diverted through the line RCL, thus enabling printer signals to be received and transmitted simultaneously. The relay F, Fig. 1, closes three circuits converging at the point a (1) for printer's lamp indicator 28, (2) for lamp 27 to indicate to exchange operator that she can monitor the receiving channel RCL by plugging into the adjacent jack MJ, and (3) for relay K which shorts the technical operator's printer transmitter TP<1> to prevent the two transmitters TP, TP<1> from being used simultaneously. Before transmitting, the operator of the instrument TP operates the key RSK to energize relay H. A relay D in the sleeve circuit of the jack TCJ has pulled down its armature, so that a circuit is made through relays G, C. Relay G maintains the circuit of lamp .28 which would have been opened by relay H, and relay C by shorting a resistance r enables a marginal relay M to open the circuit of relav U and to extinguish the lamp 27. When the system is being used for telephony and the operator of printer TP desires to use the system, the request key RSK is pressed and relay 1-1 closes a circuit through relays G and A, lighting the lamp 25 associated with the jack TCJ. When the exchange operator plugs in to jack TCJ, relay D is energized, extinguishing the lamp 25. Also relay M is fully energized, and the supervisory relay U and lamp 27 are prevented from actuation. If the exchange, operator wishes to break in immediately on the printer operation, the cord CC is taken down from the jack TCJ, thereby releasing the relays PR and F. The circuit is thus returned to normal condition for telephony, and the printer's lamp 28 and monitoring lamp 27<1> are extinguished. If the exchange operator is willing to wait for the, completion of a printer message, she operates a key RLK causing intermittent flashing of the printer's lamp 28. When his message is finished, the printer restores his request key RSK, releasing relays H, G, and C. Marginal relay M releases, and supervisory lamp 27 glows, informing the exchange operator that jack TCJ may be disconnected. The printer operator in the control room can obtain access to the line. L<1> independently of the exchange operator by connecting an auxiliary cord circuit PC to the jacks CBJ, CBJ<1>. A relay E energized over the sleeve circuit throws the tone generator O into circuit with the jack CBJ. The relay PR is energized and functions as above described. Relay F also operates, but owing to the contacts of relay E having been changed, its effect is now to light the control room lamp 29, and the various circuits converging at the point a are not affected. Printer signals can now be sent out from the control room either bv the keyboard sender TP<1> or by the tape sender TS. The arrangements described above permit the reception of printer messages whether the printer senders are in operation or not. If printer signals are only to be sent in one direction at a time, the receiving loop RPL may be disconnected and the armature of the receiving relay RR connected to the mid-point of the sending relay TR, as shown in Fig. 3. The receiving elements R of the combined instruments TP, TP<1> then record both the received and the transmitted messages.