TELEPHONE EXCHANGER
PURPOSE:To realize the detection of hook-off of a telephone set in braodcasting, by applying a DC bias at an input terminal of a broadcast sound applied to a subscriber circuit, in an exchanger providing subscriber circuits between telephone sets and crossbar switches. CONSTITUTION:When a caller hoo...
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Zusammenfassung: | PURPOSE:To realize the detection of hook-off of a telephone set in braodcasting, by applying a DC bias at an input terminal of a broadcast sound applied to a subscriber circuit, in an exchanger providing subscriber circuits between telephone sets and crossbar switches. CONSTITUTION:When a caller hooks up a handset with a broadcast audio signal instructing signal not applied at a terminal 30, a hook switch 22 is closed, a current flows from -24V at a terminal 28 to a relay 70 of a subscriber circuit 4 and contacts 71-74 are contacted, terminals 40 and 41 go to OV, hook-off is informed to a central controller (not shown) of an exchanger and if a called party is not busy, since a relay 60 is operated, a relay 50 is not activated even if the instruction signal is applied to the terminal 30, and no broadcast sound can be listened to the subscriber. If a subscriber 1 is not busy, when the instruction signal is applied to the terminal 30, the relay is activated, contacts 51-53 are contacted and the broadcast audio from terminals 31 and 32 is generated from a speaker 20 of the subscriber 1. When the telephone set is hooked up while the broadcast, the relay 70 is activated with the DC bias between the terminals 31 and 32 and the system is restored to the original state. |
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