Electronic telephone device

Details Electronic telephone device Electronic telephone device

1991-04-04

1993-01-26

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Substation originated

379418, H04M 126

Patent

active

051827670

ABSTRACT:
The device includes an acoustic transmitter (10), a tone generator (12), a memory (14) containing an identification code (N) and a service key (C), and an electronic circuit (16). A digital message transmitted depends on N and C and changes with each use. The time limitation moment of the device is determined. The device appears in the form of a token.

REFERENCES:
patent: 4126768 (1978-11-01), Grenzon
patent: 4677657 (1987-06-01), Nagata et al.
patent: 4817135 (1989-03-01), Winebaum
patent: 4941172 (1990-07-01), Winebaum et al.
patent: 4980910 (1990-12-01), Oba et al.
patent: 4988987 (1991-01-01), Barrett et al.
patent: 4995077 (1991-02-01), Malinowski

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