Operator Supervisory Circuit for a Key Telephone System

This invention relates to telephone systems and more particularly to a key telephone system.

During the course of the following description and when reading the claims, it should be remembered that due to the design and operation of a key telephone system there is a ground employed therein which is actually a positive voltage and is referred to herein as key system positive ground or merely positive ground.

In presently known key telephone systems, which incorporate a rather large number of central office lines, the operator, after placing the operator subset on hold and dispersing the calls to a called party, would have no means of knowing whether calls were answered and placed back on hold by the called party.

An object of the present invention is to provide an operator supervisory circuit for a key telephone system which would advise the operator when the called party has answered and also when the called party has placed his subset on hold.

A feature of the present invention is the provision of an operator supervisory circuit for a key telephone system comprising: a source of key system positive ground; an operator's subset coupled to the source; a called party's subset; a supervisory indicator lamp; a line button lamp; and a switching arrangement coupled to the operator's subset, the source, the indicator lamp and the line button lamp to lit the indicator lamp when the operator's subset is taken off-hook to answer an incoming call, to cause the line button lamp to wink when the operator's subset is placed on hold to disperse the incoming call to the called party's subset, to extinguish the indicator lamp and the line button lamp wink when the called party's subset is taken off-hook, and to cause the line button lamp to again wink when the called party's subset is placed on hold after the called party's subset has been taken off-hook.

The above-mentioned and other features and objects of this invention and the manner of obtaining them will become more apparent by reference to the following description taken in conjunction with the drawing, the single Figure of which is a schematic diagram partially in block form of the operator supervisory circuit in accordance with the principles of the present invention.

On incoming calls the regular line button lamp LI flashes due to circuitry not shown until the incoming call is answered. When the call is answered at the operator's subset OS, the key system positive ground is applied to the operator's subset "A" lead LD1 through normally closed hold switch S2 and hookswitch S1. This key system positive ground is passed through forward biased diode D1 to operate relay RL1. The positive ground is also passed through the forward biased diode D2 to line card LC which illuminates line button lamp L.sub.1 through contacts C.sub.6 due to circuitry not shown on line card LC. When relay RL1 is actuated, contacts RL1.sub.1 and RL1.sub.2 are moved into the position opposite to that shown. Contact RL1.sub.2 applies a normal ground to indicator lamp L2 for illumination thereof. Contact RL1.sub.1 provides a hold path for relay RL1 when the operator's subset is put on hold. This holding path for relay RL1 is provided by contact B6 when relay B on the line card LC, not shown, is actuated. The positive ground for the key system is coupled to a contact of the contact set RL1.sub.1 by a forward biased diode D3. This same positive ground is coupled by forward biased diode D4 to relay RL2 which closes contact set RL2.sub.1 to actuate interrupter motor IM which makes and breaks the contact of switch S5 coupled to line button lamp L1 to thereby cause this lamp to wink. Capacitor C1 in shunt relation to relay RL1 slows up the release of this relay so that relay B on line card LC, not shown, will have time to operate and apply positive ground to the holding path for relay RL1. Thus, when the operator's subset is put on hold by hold switch S2, in order to disperse the call, hold switch S2 is placed in an open position removing positive ground from lead LD1, supervisory indicator lamp L2 is lit by actuation of relay RL1 and is maintained actuated by the holding circuit of contacts RL1.sub.1. At this time the line button lamp L1 is winking.

When the called party picks up his subset hookswitch S4 closes thereby deactivating relay B due to circuitry not shown on line card L.C. and removes the positive ground through diode D3 to the hold circuit contacts of relay RL1 causing this relay to deactivate and to be returned to the position illustrated and, thereby, extinguish the supervisory indicator lamp L2 which notifies the operator that the called party is now connected through or has answered his subset.

Should the called party now put his subset back on hold, the supervisory indicator lamp associated with that line would not light, although the regular line button lamp would begin to wink once again. This would then indicate to the operator that the called line was answered and put back on hold by the called party. This is accomplished by the called party opening hold switch S3 which again removes a positive ground from the line card and allows relay B to actuate which closes contact B6. This positive ground is then applied to diode D4 to relay RL2. When relay RL2 is operated, a normal ground is applied to the interrupter motor IM which in turn operates switch S5 to cause lamp L1 to wink. When the called party is taken off hold by closing switch S3, contact B6 opens removing the ground from the line start lead LD2 thereby releasing relay RL2 and returning the circuit to the idle condition.

While I have described above the principles of my invention in connection with specific apparatus it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claims.