Patent GB-1437483-A (GB)
Title: Operator display arrangements of a telephone exchange switching system
IPC: H04Q3/62
Filed: 1973-04-19
Abstract: 1437483 Automatic exchange systems; cathode-ray tube displays GTE INTERNATIONAL Inc 29 Jan 1974 [19 April 1973] 19183/73 Headings H4K and H4T In a PABX, an operator's line-status display comprises a CRT tube or an LED matrix. The tube/matrix is scanned in conjunction with a line address generator such that each area of the display corresponds to a particular line and the condition (or conditions) of each area represents the line status, e.g. busy, free, calling, parked, class of service such as out of service, executive cut-in or trunks barred, or under test. The various states for each line may be displayed by, e.g. modulating the electron beam such that corresponding symbols or words appear on that tube face area corresponding to the line. These states may be displayed singly in dependence on which particular facet of the current exchange operation the operator wishes to see by appropriate actuation of her keyset or they may be displayed simultaneously. The brightness of the display may be adjusted automatically by an FET and photoresistor circuit. For full details of the PABX system attention is drawn to Specification 1,374,635. Incoming exchange line call. The line supervisory ELS responds to the call by flashing a lamp CL on an operators board OC. She actuates her coupling key KLC so as to bring up OC in the exchange line unit pertaining to the calling line and also her speech key so that she may converse with the caller. She then couples her board to a register unit OR by actuating key KOC so that she can dial or key the wanted extension number into the register store STO. Alternatively she may press her light pen PAM (Fig. 3) against the CRT position RA or the LED matrix co-ordinate MLD corresponding to the wanted extension so that when this position or co-ordinate is scanned a pulse is extended over l21 to her board and thence to the register unit so as to stop the scanning of the PBX extension line circuits at the position of the wanted party. The presence of the dialled number in store STO has the same effect by virtue of comparator CA which is fed with the scanned extension addresses over highway E1D. In the stopped position of the scanner the address thereon is written into store STE in the exchange line unit. A connection to the wanted extension is then set up automatically via switch SW. The operator actuates her ringing key and scanning restarts. At the end of the scan cycle all the units, apart from the exchange line unit, are released. The operator's line condition keyset KA-KG (Fig. 3) permits an immediate display of any particular condition for all the extensions. The references B-TP indicate the different conditions as mentioned earlier apart from CI which provides the identity of the extension connected to an exchange line to which the operator is currently coupled via an exchange line unit. A temporarily moved extension may be displayed. The ambient light control circuit (Fig. 4) incorporates a variable pulse width gate LCG in the lead l31 extending to the CRT control grid. The gate is controlled in dependance on the conductivity of an FET having a photo-cell LDR connected to its gate electrode.