Patent GB-1198103-A (GB)
Title: Telephone System
IPC: H04M3/58
Filed: 1967-08-29
Abstract: 1,198,103. Automatic exchange systems. TELEFON AB L.M. ERICSSON. 29 Aug., 1967 [6 Sept., 1966], No. 39452/67. Heading H4K. . In an exchange system having some subscribers who are provided with key sets, operation of a special key by a subscriber who is taking part in a call leads to the automatic identification of the calling and called parties, the storage of their identities in a memory and the subsequent breaking down of the existing connection. The facility may be used for the purposes of call transfer or paging but the details of how these types of call are set up after the existing call has been broken down are not disclosed. The substations are of the loud-speaking variety and are interconnected by a four-wire transistor or relay switching network. Particular description.-It is assumed that subscribers 1 and 2 are in communication and consequently that the following components are operated: individual relays BRA, BRB; crosspoints KVA, KVB; and line relays AH, BH. The four-wire lines are connected via an audio link SNR which includes a called side feed-bridge SMB and a calling side feed-bridge SMA, the latter being supplied with positive potential over the winding 28 of an unenergized relay R0. If subscriber 1 now operates his special key 7, similarly poled rectifiers 63, 64 effectively short circuit the G0 loop Aa, Ab and consequently relay R0 comes up. R0 holds temporarily through the discharge of capacitor 150. Consequently special service identification relays RR1-RR4 are connected to the G0 loop. These relays are shunted by rectifiers and are connected together in such a way that only two of them will come up in response to the operation of a special key 7, RR2, RR3 being operable in this case. Operating current for these relays is derived from an A.C. transformer TR. With RR2 and RR3 up, a particular contact chain 79-76 is closed whereby a particular function relay 75 is energized and held, to - ve  over one of its own contacts. Line relays AH, BH and individual relays BRA, BRB fall back but the hold windings 124, 125 of the crosspoints KVA, KVB are maintained energized via the - ve  potential applied to contact 85 of relay RO. Closure of relay 75's leftmost contact applies a start potential via relay contact chain 87-90 to tens and units called-partyidentification-start relays IBT and IBE. Consequently - ve  identifying potential is applied from contact 93 over wire 94, contact 95, wires 96, 96a, break-contact 97 of subscriber 2's individual relay BRB, wire 98 to the called party's diode/relay translation and storage circuit. Two BM relays e.g. 101 (tens) and 105 (units), come up and hold over their second windings 103, 107. With the identity of the called party now stored on the BM relays a start potential is applied over lead 113 to a similar translation and storage circuit AM where the identity of the calling party is recorded. Thereafter, the holding potential for function relay 75 is removed, thus bringing down R0 (which was held over contact 81) and releasing the crosspoints KVA and KVB. All the other operated relays, except the two in each storage circuit, fall back and a new connection from subscriber, in accordance with the function (special service) "requested" by his special key, is set-up.