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 NL269292ApublicationCriticalpatent/NL269292A/xx
H04M1/00—Substation equipment, e.g. for use by subscribers
H04M1/26—Devices for calling a subscriber
H04M1/30—Devices which can set up and transmit only one digit at a time
H04M1/50—Devices which can set up and transmit only one digit at a time by generating or selecting currents of predetermined frequencies or combinations of frequencies
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04M—TELEPHONIC COMMUNICATION
H04M1/00—Substation equipment, e.g. for use by subscribers
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04M—TELEPHONIC COMMUNICATION
H04M19/00—Current supply arrangements for telephone systems
H04M19/02—Current supply arrangements for telephone systems providing ringing current or supervisory tones, e.g. dialling tone or busy tone
H04M19/04—Current supply arrangements for telephone systems providing ringing current or supervisory tones, e.g. dialling tone or busy tone the ringing-current being generated at the substations
H—ELECTRICITY
H04—ELECTRIC COMMUNICATION TECHNIQUE
H04Q—SELECTING
H04Q1/00—Details of selecting apparatus or arrangements
H04Q1/18—Electrical details
H04Q1/30—Signalling arrangements; Manipulation of signalling currents
H04Q1/44—Signalling arrangements; Manipulation of signalling currents using alternate current
H04Q1/444—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies