Digital supervisory circuit for a telephone system

Details Digital supervisory circuit for a telephone system Digital supervisory circuit for a telephone system

1982-04-26

1984-06-19

Brown, Thomas W.

H04M 322

Patent

active

044554567

ABSTRACT:
The digital supervisory circuit comprises an amplitude comparator and EXCLUSIVE-OR gate to provide an output signal indicating the difference in time an input signal is above and below a predetermined reference potential. This output signal is integrated in an up-down binary counter and also is coupled to a first logic circuit under control of the counter which provides a ring present supervisory signal when a first threshold is exceeded and a second logic circuit under control of the counter which provides a switch hook detection supervisory signal when a second threshold is exceeded. A hit-timing circuit is provided coupled to the counter and the first and second logic circuits to prevent response of the counter and second logic circuit to line transients.

REFERENCES:
patent: 3772477 (1973-11-01), Richards
patent: 4022980 (1977-05-01), Kitajewski et al.
patent: 4087646 (1978-05-01), Brolin et al.
patent: 4362908 (1982-12-01), Melindo
"Active Transformers for Off-Hook Sensing in Telephone Applications", Bajorek et al., IEEE Trans. on Magnetics, vol. MAG-14, No. 5, Sep. 1978, pp. 1062-1064.

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