Telephone device for preventing a long-term on-line state result

Details Telephone device for preventing a long-term on-line state result Telephone device for preventing a long-term on-line state result

1997-05-09

1999-07-13

Le, N.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379387, 379 33, 335175, 335179, H04M 100, H01H 900

Patent

active

059237481

ABSTRACT:
A telephone device for preventing a long-term on-line state resulting from the handset being unintentionally left off-hook. The device preferably includes: a telephone line interface circuit serving as an interface between a ring line and a tip line, and an internal circuit; a ringing detector for sensing a ringing signal; a hybrid circuit dividing connecting ends of the telephone line interface circuit into an input end and output end; a dual-tone multi-frequency generator generating a dual-tone multi-frequency signal; a controller controlling the telephone line interface circuit to execute an automatic on-hook operation; a push-button pad outputting a control signal or numerical signal to the dual-tone multi-frequency generator in order to represent a pressed key by using a dual-tone multi-frequency signal; a switch controlled by the dual-tone multi-frequency generator, wherein a sound signal from a handset is interrupted as soon as the dual-tone multi-frequency generator outputs a dual-tone multi-frequency signal; a receiver off hook tone detector detecting a receiver off hook tone, wherein a signal is delivered to the controller when a receiver off hook tone is detected, and the controller thereby triggers the telephone line interface circuit into an automatic on-hook state; and a handset for receiving and transmitting the sound signal.

REFERENCES:
patent: 4063299 (1977-12-01), Monroe
patent: 4849846 (1989-07-01), Hung et al.
patent: 4922529 (1990-05-01), Kiel
patent: 5606593 (1997-02-01), Smith
patent: 5612997 (1997-03-01), Vallelunga, Sr. et al.

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