Patent GB-531394-A (GB)
Title: Electrical communication system
IPC: H04M11/06
Filed: 1939-07-11
Abstract: 531,394. Diplex telegraphy ; electric synchronous movements. ELECTRICAL RESEARCH PRODUCTS, Inc. July 11, 1939, No. 20130. Convention date, July 19, 1938. [Class 40 (iii)] [Also in Group XXXIX] In a two-way system in which for each direction of transmission telephony and code telegraphy take place alternately, the telegraph sender at the near end and receiver at the far end being disconnected by voice-controlled switching apparatus, a code cycle which has been partially transmitted when disconnection occurs is stored and subsequently retransmitted, but if only a single element remains to be sent (the disconnection is delayed to allow the completion of the cycle. : The invention is applied to a system including radio links, with diplex telegraphy under the control of synchronous distributers which are arranged to start transmission only at. the beginning of a: code-cycle. A master relay 49. is energized through an amplifier-detector 48 by speech in the transmitting path 40 and connects up relays 68, 69, 53, 104 and 111. Relay 53 removes a shunt from a singing suppressor 51, 52 and thus allows the speech to pass through a delay and amplifying circuit 50 to the radio transmitter T. Relay 111 connects. control current of two frequencies, e.g. 150, 3000 cycles, to the transmitter T. Relay 69 disables the control current path associated with the radio receiver R, while relay 104 stops telegraph transmission as described later. Incoming control current from the receiver R passes to an amplifier-detector 118 and energizes relays 119-122. Relay 120 removes a shunt from a singing suppressor 123, 124 and allows speech to flow through a delay and amplifying circuit 128 to the receiving path 41. Relay 122 disables the transmitting path at a suppressor 44, 45 while relay 121 disconnects relay 129 to stop telegraph reception as described later. Two five-pin tape transmitters A, B alternately control a polar relay 79 by connecting spacing or marking current thereto over consecutive contacts of the distributer 65, and relay 79 when energized to its marking position connects telegraph current of two frequencies, e.g. 935, 2295 cycles to the radio - transmitter T. Two frequencies are employed both for telegraphy and for voice-control to avoid selective fading. The tape of each transmitter is advanced by a circuit over segment 97 or 99 during the transmitting cycle of the other, provided a corresponding relay 92 or 105 is in position. When relay 104 energizes on the initiation of speech, relays 86, 87 pull up, connecting steady spacing current to relay 79 and grounding ring 81, so that as the distributer advances relays 92, 105 operate over their upper windings to spacing position; and the tapes remain stationary. The marking circuits of relays 92, 105 through their lower windings pass over contacts 91, 106, so-that telegraphy can restart only at the beginning of a code cycle. If however relay 104 energizes while the final elements of a cycle is being sent, relays 88, 89 are operative over a contact 107, and the control by 104 is disabled until the distributer moves beyond that contact, while the circuit for sending voice-control current is disabled at transformers 109, 110. The delay ;is less than that introduced by the circuit 50 and seldom results in clipping of speech. The telegraph receiving. relay 154 fed through an amplifier-detector 153 controls relays 155, 169, 156, and marking current is connected over consecutive contacts of the distributer 158 to the selecting magnets, of two printers A, B in turn, and the printing magnet of each operates over. a segment 173 during the receiving cycle of the other. When relay 129 is disconnected by the arrival of voice-control current, relays 150, 165 pull up; holding relays 155, 169, 156, in spacing position and applying battery to ring 166 so that as the distributer advances relays 167 operate over their upper windings to spacing position and open the printing circuits. Relay 169 controls over segments 171 the return of relays 167 to marking position when telegraphy restarts. At each marking operation relay 156 connects a condenser which is charged during spacing to ring 176, which is connected alternately to the windings of a balanced relay 179. Lack of synchronism between the sending and receiving distributers will be indicated by operation of one or the other of relays 180, 181.