Patent GB-516615-A (GB)
Title: Improvements in and relating to electrical communication systems
IPC: H04W84/02
Filed: 1938-03-29
Abstract: 516,615. Manual exchange systems ; high-frequency transmission. TELEPHONE MANUFACTURING CO., Ltd., and PADDLE, L. H. March 29, 1938, No. 9578. [Class 40 (iv)] [Also in Group XL] The transmitting valves of a wireless link in an inter-exchange junction are switched on when a calling signal is applied to the junction, two co-operating. wireless transmitters and receivers provide two-way communication and both transmitters are normally inoperative and are placed in operation by means responsive to the calling signal. Calling arrangements. When a plug is inserted in jack JS (Fig. 2) at station A relay S operates followed by BU and V and, for the operating time of thermal relay THA (about one second), 17 cycle ringing current is applied to the line leading to the wireless transmitting station B. Relay R (Fig. 3) at station B responds and relay OG pulls up, followed by SA, SR and SO. Relay SO switches on the anode current to transmitting valve TV and relay AN in the valve anode circuit responds. When the ringing signal terminates relay R falls away and relays SX and TY pull up. Relay TY connects an answering signal of frequency Y (750 cycles) to station A and relay SX connects a signal of frequency X (600 cycles) to the distant station C over the radio link. The equipment at station C is similar to that at B (Fig. 3) and that at D similar to that at A (Fig. 2). At station C the X signal causes relay UX to pull up followed by IC. The anode circuit of the transmitting valve is completed at IC1 and relay SY is operated so that a signal of Y frequency is sent back to station B where relay UY pulls up followed by relay PA which opens the circuits of SX and TY to stop transmission of signals from B to station A and C. At station C relay UX releases and relay TR is energized to connect ringing signal to station D. After about one second relay TH pulls up to energise QA and release TR so that ringing stops. At station D relay L responds to the ringing signal, relay LR pulls up and calling. lamp LL is lit. When the operator plugs into the circuit, relay S energises and IC operates to release relay LR and relay BU energises. Re-ringing. If the called operator rings on the circuit relay A responds and V pulls up to connect ringing current to the line. At station C relay R responds and SX energises to connect X current to the radio link. At station B relay UX pulls up and TR is energised to connect ringing current to the circuit to station A where relays L and LR respond to light lamp LL. Release. When the calling operator unplugs relay S releases and V energises to connect ringing current to station B. Thermal relay THB energises after 10 seconds and relays BU, LR and HA fall away. At station B relay R. responds to the ringing current and remains energised for 10 seconds. After its time delay of three seconds relay SA falls away followed by SR and OG. Relays SX and SY energise to connect X and Y current to station C. After 10 seconds relays R, SO, PA, SX and SY fall away and the apparatus is again normal. At station C relays UX and UY are energised together so that relay QC energises, OG releases and TR pulls up to connect ringing signal to station D. At station D lamp LL lights and when the plug is withdrawn relays S, L, LR, BU and IC release. Unsuccessful call. If transmission from B to C is unsuccessful continuous tone is sent from B to A, the frequency depending on whether relay AN has or has not operated.