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 NL235237ApublicationCriticalpatent/NL235237A/xx
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
H04Q1/45—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling
H04Q1/453—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling in which m-out-of-n signalling frequencies are transmitted
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Engineering & Computer Science
(AREA)
Computer Networks & Wireless Communication
(AREA)
Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo
(AREA)
Digital Transmission Methods That Use Modulated Carrier Waves
(AREA)