Patent GB-1431937-A (GB)
Title: Communication systems
IPC: H04M3/60
Filed: 1973-07-23
Abstract: 1431937 Automatic exchange systems WESTERN ELECTRIC CO Inc 23 July 1973 [27 July 1972] 34900/73 Heading H4K Calls requiring assistance are each connected with an operator via a loop circuit which provides line loop facilities and acts as a supervisory junctor and the arrangement is characterized in that each operator position has a number of dedicated loop circuits and in addition there is provided a pool of shared loop circuits any one of which may be utilized by a call to an operator position when the dedicated loop circuits of that position are all in use, such a situation occurring when one operator has a number of calls on "HOLD". Any of the operators can be selected to deal with any request for service. The arrangement is utilized in a generally known type of PBX having four operator positions 128-, each operator having two dedicated loop circuits, e.g. 116-0A, 116-0B, and having access to a pool of four shared loop circuits 116-0 to 116-3, with sharing circuits 118- arranging the four operators in a different order of preference for each shared loop circuit. Demands for operator assistance from the network are passed to a loop preference circuit 105B, this circuit ensuring that an idle dedicated loop circuit associated with a free operator is chosen in preference to a shared loop circuit. An operator dealing with a call is considered busy unless that operator has placed the call on "hold", and where the available free operators have both their respective dedicated loop circuits occupied with "holding" calls an idle shared loop circuit is selected. Figs. 2A, 2B (not shown) illustrate the arrangement of the sharing circuits with each sharing circuit (Fig. 3, not shown) including an arrangement of four relays and their associated contacts for indicating the order of preference and controlled by a further two relays (X and Y) which indicate whether 1, 2, 3 or 4 of the positions are busy. Fig. 4 shows one of the loop circuits and its connections with an operator position and the network. Following a request for service from a central office trunk circuit 403- a connection is established from the trunk circuit to a chosen loop circuit over wires T1R1 via trunk access network 405 and a lamp is lit at the corresponding operator position. The operator depresses a pickup key PU to complete a speech connection from her headset over wires TA, RA, transformer T, wires T1R1 to the calling trunk T.R. A connection is completed to a requested PBX extension by the depression of a start key and the performance of the required dialling operations. A connection is established through the network 101 or wires T, R, S and via wires T2R2 to transformer T1 enabling the operator to converse with the called party. If no further assistance is required, a release key is depressed thereby causing the removal of a line split at contacts CON and the dropping of the connections between the loop circuit and the network/ trunk circuit and between the operator and the loop circuit. A call from a PBX extension to the operator is dealt with in a similar way using an attendant trunk circuit 404. The Specification also describes a similar operation for an operator initiated call.