Data transmission system of key telephone system

Details Data transmission system of key telephone system Data transmission system of key telephone system

1987-03-23

1988-12-27

Ng, Jin F.

Telephonic communications

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

Switching or supervision feature

H04M 172, H04Q 300

Patent

active

047946415

ABSTRACT:
A system for transmissing data by a pulse signal through a pair of lines connected between a main unit and a key telephone set is disclosed. The main unit includes a transmitter for sending, prior to transmission of pulse train data, a start signal of a pulse train including a pulse of an n-bit (where n is an integer) specific logic value and a pulse of an (n+1)-bit logic value opposite to the specific logic value. The key telephone set includes a change detector for detecting a change in the pulse train of the start signal in a direction of the logic value opposite to the specific logic value, a logic value detector for detecting a logic value of an (n+1)th bit pulse from a detection timing of the change detector, a discriminator for discriminating on the basis of the logic value of the (n+1)th bit pulse whether a line connection for the key telephone set is normal, and a reader for reading data following the start signal according to a logic determined by a discrimination result.

REFERENCES:
patent: 4181909 (1980-01-01), Pyeatte
patent: 4514597 (1985-04-01), Kikuchi et al.
patent: 4551583 (1985-11-01), Sekiguchi
patent: 4564726 (1986-01-01), Ibata
patent: 4583214 (1986-04-01), Miyashita

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