Telecommunication system with keyboard selection

Details Telecommunication system with keyboard selection Telecommunication system with keyboard selection

1977-11-22

1978-12-19

Robinson, Thomas A.

H04M 300

Patent

active

041307364

ABSTRACT:
A terminal of a radio link or other two-way channel incapable of transmitting d-c signals, extending to a remote exchange, serves a multiplicity of local subscribers having keyboard-equipped telephone sets generating multifrequency selection signals accompanied by a d-c key signal. A detector at the terminal, responding to the arrival of a key signal from a calling subscriber line, connects that line to the outgoing channel to facilitate the transmission of the selection signals to the exchange; upon the arrival of an answer criterion from the exchange, the receiving branch of the channel is extended by another detector to the calling subscriber line.

REFERENCES:
patent: 2665375 (1954-01-01), Collyer et al.
patent: 3426154 (1969-02-01), Finkhauser et al.

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