Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Publication of BE484143ApublicationCriticalpatent/BE484143A/xx
H04M1/00—Substation equipment, e.g. for use by subscribers
H04M1/64—Automatic arrangements for answering calls; Automatic arrangements for recording messages for absent subscribers; Arrangements for recording conversations
H04M1/65—Recording arrangements for recording a message from the calling party
H04M1/654—Telephone line monitoring circuits therefor, e.g. ring detectors