Key telephone system provided with telephone sets connectable to

Details Key telephone system provided with telephone sets connectable to Key telephone system provided with telephone sets connectable to

1992-01-24

1993-06-29

Schreyer, Stafford

Telephonic communications

Multi-line or key substation system with selective switching...

Switching or supervision feature

379166, H04M 172

Patent

active

052241599

ABSTRACT:
Disclosed is a key telephone system provided with a key service unit (KSU) 1 having a central control unit 6, and a digital key telephone set (DKT) 10 having a local control unit 13 for communications of control data with the central control unit 6. First and second add-on modules (ADMs) 24 and 34 for communications of control data with the central control unit 6 are optionally connectable to the DKT 10. When control data (up-data) are transmitted from the local control unit 13 of the DKT 10 to the KSU 1, a disable signal is given from the DKT 10 to the first ADM 24 to disable up-data from being transmitted from the first ADM 24. At this time, the first ADM 24 also outputs a disable signal to the second ADM 34 to disable up-data from being transmitted from the second ADM 34. At any selected time when no up-data are transmitted from the DKT 10, an enable signal is given from the DKT 10 to the first ADM 24. In response to this enable signal, when up-data to be transmitted from the first ADM 24 are present, the first ADM 24 transmits the up-data and further gives the disable signal to the second ADM 34 to disable up-data from being transmitted from the second ADM 34. On the other hand, in response to the enable signal from the DKT 10, when up-data to be transmitted from the first ADM 24 are absent, the first ADM 24 outputs an enable signal to the second ADM 34 to enable up-data to be transmitted from the second ADM 34.

REFERENCES:
patent: 4932043 (1990-06-01), Nakayama et al.

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