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 BE492617ApublicationCriticalpatent/BE492617A/xx
H04Q1/00—Details of selecting apparatus or arrangements
H04Q1/18—Electrical details
H04Q1/30—Signalling arrangements; Manipulation of signalling currents
H04Q1/32—Signalling arrangements; Manipulation of signalling currents using trains of DC pulses
H—ELECTRICITY
H03—ELECTRONIC CIRCUITRY
H03K—PULSE TECHNIQUE
H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
H03K17/28—Modifications for introducing a time delay before switching
H03K17/288—Modifications for introducing a time delay before switching in tube switches
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