Guard circuit for ground start telephone equipment

Details Guard circuit for ground start telephone equipment Guard circuit for ground start telephone equipment

1976-07-02

1977-04-12

Cooper, William C.

H04M 710

Patent

active

040176908

ABSTRACT:
A guard circuit is designed to be inserted in a two wire trunk between a central office and customer terminal equipment for the purpose of reducing the time period that the customer terminal equipment, for example, a private automatic branch exchange (PABX), is subject to glare. Essentially, the guard circuit monitors the various potentials of the two wire trunk from the central office. Upon release of an established connection from the central office, ground is removed from the positive line and negative potential is applied to the negative line. The guard circuit recognizes this change in potential and separates the customer terminal equipment from the central office until the customer terminal equipment is released and reconditioned. Glare cannot occur during the separation interval and thus the time period during which glare could occur is substantially reduced.

REFERENCES:
patent: 3491213 (1970-01-01), Gilboy et al.
patent: 3700822 (1972-10-01), Fritschi

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