| 摘要 |
The invention refers to that type of telephone exchange installations which comprises protection relays (17, 18) which when operating current failure occurs shunt the exchange installation (8, 9, 10) and connect an extension (14) directly to an associated telephone line network (15). The invention solves the problem of using such installations when the wish is to interconnect two exchanges through a private or leased line (15', 15') in such a way that one (18') of the relays (11') is controlled by a programmable computer circuit (21', 22', 23') which circuit is connected to an extension line circuit 19'). The arrangement is such that external incoming calls are directed to said extension line circuit (9') while outgoing calls are directed from the central line (10') of the exchange (8') to said network (15'). |
