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 BE252855ApublicationCriticalpatent/BE252855A/xx
H04M3/08—Indicating faults in circuits or apparatus
H04M3/14—Signalling existence of persistent "off-hook" condition
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04M—TELEPHONIC COMMUNICATION
H04M3/00—Automatic or semi-automatic exchanges
H04M3/08—Indicating faults in circuits or apparatus
H04M3/12—Marking faulty circuits "busy"; Enabling equipment to disengage itself from faulty circuits ; Using redundant circuits; Response of a circuit, apparatus or system to an error
