Patent GB-871554-A (GB)
Title: Improvements in or relating to direct call telephone systems
Inventor: CORNER ARTHUR CHARLES
IPC: H04M9/00
Filed: 1958-10-29
Abstract: 871,554. Interconnection systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Oct. 7, 1959 [Oct. 29, 1958], No. 34602/58. Class 40 (4). In an interconnection system having a common speech circuit for internal calls and having access to two external lines, for example one to a public exchange and one to a PAX, each station is provided with a terminal block TB to which are wired the telephone instruments including keys and lamps, and also a relay set SRS. The stations are interconnected serially by multiple cables CPS, CSS, and the exchange lines ELA, ELB are connected to station 1 only and are advanced from station to station by way of relay contacts to the last station 5 where common answering equipment (Fig. 3) is located. Inter-station calling is effected by keys KC1 . . . KC5, the buzzer BZ of each station being connected over lead LX to the appropriate terminal 1 . . . 5. Relay C operates at the calling station and holds under control of switchhook contact SHC, and speech takes place over the common circuit C-, C+ which is fed with current from the common equipment. Outgoing calls.-Key KA which relates to the exchange line ELA operates relay A which loops the line and lights lamps LPA at all stations. The wanted call is set up by dialling, and cancel key KCL allows release of the exchange equipment if an error is made. Key KE provides for recalling an operator in certain circumstances. Key KB which relates to the exchange line ELB operates relays B, R to loop the line and light lamps LPB. Incoming calls.-These are normally answered at station 5 where lead XB is connected to terminal XB and key KX is actuated. At stations 2 . . . 4 lead XB is connected to terminal XA so that terminals XB at stations 4 and 5 are connected together. The answering facility may, however, be transferred by connecting terminal XA at station 5 to the appropriate terminal 1 . . . 4. If key KX at station 5 is not restored the buzzers BZ at both stations will be in circuit. Assuming an incoming call over line ELA, relay RA, Fig. 3, responds to ringing current and relays FA, FB interact to sound the buzzer BZ at the answering station and to flash lamps LPA at all idle stations. The actuation of key KA operates relay A which trips the ringing and lights the lamps steadily. To transfer the call one of keys KC1 . . . KC4 is actuated, and relay C makes a local connection while holding the exchange line, lamp LPA flashing at the answering station. On the actuation of key KA at the wanted station relay A operates to connect that station to the exchange line instead of the answering station. If the call is not accepted reoperation of key KA at the answering station releases relay C. An incoming call over line ELB is dealt with similarly, lamps LPB and keys KB being effective. Local call while exchange call is held.-Since the actuation of a calling key KC1 . . . KC5 operates relay C, the exchange call is held and the exchange line lamp flickers. The local call may be cleared by re-operation of the exchange line key. Alternatively the exchange call may be transferred to another station by the actuation of the exchange line key thereat. A party engaged in an exchange call may answer a local call by actuating the calling key relevant to his own station, and may return to the exchange call by actuating the exchange line key. Station engaged on exchange line ELA makes call over exchange line ELB.-The operation of key KB connects up relays B, BR without releasing A, so that the call on line ELA is held. Thus an enquiry call may be set up over line ELB, being cleared by reoperation of key KA.