Telephone line monitoring circuits therefor, e.g. ring detectors

Full Title

Substation equipment, e.g. for use by subscribers > Automatic arrangements for answering calls; Automatic arrangements for recording messages for absent subscribers; Arrangements for recording conversations > Recording arrangements > Telephone line monitoring circuits therefor, e.g. ring detectors

Classification Context

Section:

ELECTRICITY

Class:

ELECTRIC COMMUNICATION TECHNIQUE

Subclass:

TELEPHONIC COMMUNICATION