Patent GB-914386-A (GB)
Title: Improvements in or relating to private automatic branch exchanges
Inventor: CURTIS GERALD
IPC: H04M15/34
Filed: 1961-09-12
Abstract: 914,386. Automatic exchange systems. AUTOMATIC TELEPHONES & ELECTRIC CO. Ltd. Sept. 12, 1961, No. 32658/61. Class 40 (4). A private automatic branch exchange has facilities for automatically producing a printed record of the particulars of calls completed over a group of lines extending to a public exchange network. The record concerns calls made from an extension employing the initial digits 8 and 7. Calls over the local area of the public exchange are not recorded when day working is in force and these calls are obtained by dialling the initial digit 9. With day working in force trunk calls are set up by an operator whose assistance is obtained for an extension dialling the digits 8 and 7. Having given the operator particulars the extension hangs up and the operator seizes an idle keysender to call the wanted number and the extension; the impulses produced by the keysender being monitored by the printing equipment. With night working in force a night service key at the operator's position enables 200 of the several thousand pabx extensions to dial either local or trunk calls directly over the public network which is reached with the initial digits 8 and 7. To record particulars of the call the printing equipment monitors the digits dialled by the extension and records the identity of the calling extension by means of a finder identifier. As shown in the drawing, internal calls are made from an extension such as LC by way of line finders 1LF, 2LF, group selectors 1GS and GSL, and a final selector FSL. Outgoing trunk calls are made over a group of twenty lines such as EXL each served by an exchange line relay set ERS. With day working in force contacts NS controlled by the manual board night service key are in the position shown so that an extension dialling digit 8 and 7 seizes an idle assistance relay set ARS over group selectors 1GS, 2GS. An idle operator is now connected over the connector C and control circuit CC. Having established requirements the extension hangs up and the operator clears down the connection with a release key. By means of a connect key the operator seizes an idle connector C and an exchange line relay set ERS which gives a start signal to the ticket printer control circuit TPCC and receives dial tone from the public exchange. Meter print equipment MPE and a control circuit TPCC is provided for each of the twenty relay sets ERS and as the operator transmits digits to the public exchange from a keysender KS connected over finder CCF, the impulses set a digit type wheel in the print equipment MPE. When the wanted subscriber replies over the public exchange the operator uses a speak extension key which causes line finder OLF to connect the relay set ERS in use for the call to group selectors 1GSP, 2GSO by means of which the operator gains access to the final selector FSO and the calling extension. The digits transmitted by the operator set the digit type wheel in the print equipment to record the extension number. The paper strip on which the record is made is advanced between each digit and spaced between the calling and called numbers. During the call, from which the operator retires, metering pulses are received by TPCC which drives a metering type wheel. When the connection is released the number of meter pulses received is printed together with a number identifying the printer used and an indication that day service is in force. The paper strip is advanced in readiness for the next call and the equipment is released. When night service is in force the contacts such as NS are operated so that a privileged extension may employ the digits 8 and 7 to seize an exchange line relay set ERS directly and dial the wanted number to the public exchange. This number is recorded by MPE by monitoring the impulses as with day service conditions except that the impulses are repeated by ERS through a night service digit storage circuit NSDSC. To obtain a record of the calling extension one of two alternately employed digit storage control circuits NSDSCC is taken into use and is connected to the storage circuit NSDSC corresponding to the relay set ERC involved. A line identifier control circuit LIFCC now extends a mark backwards on the D wire over ERS and the switch train and the line identifier finder LIF hunts for this mark over the 200 extensions given a night service facility. Line identifier finder LIF comprises a motor uniselector with eight banks of fifty outlets each. The banks are connected in pairs with the wipers of each pair set 180 degrees apart so as to sweep a hundred outlets in one revolution. Two pairs of banks have access to extension D terminals and are searched simultaneously for the marked terminal. The pair of banks in which the mark is found establishes the hundreds digit. The remaining two pairs of banks are connected up to mark the tens and units digits of the calling extension. When the marked extension is found, therefore, the calling extension identity is set up on two sets of four and one set of two relays in the control circuit LIFCC and is transferred over NSDSCC and NSDSF to the digit storage circuit NSDSC. At this point the identifier circuits release. When the first meter pulse is returned from the public exchange the storage circuit NSDSC seizes a key sender KS over connector CCF and controls it to transmit pulses to TPCC to set the digit type wheel in the printer MPE to print the extension number. On release, the printer records the metering pulses received, the number of the printer involved and an indication that night service was in force.