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1. (WO1979000066) MULTIFREQUENCY SIGNAL RECEIVER
Latest bibliographic data on file with the International Bureau

Pub. No.: WO/1979/000066 International Application No.: PCT/US1978/000044
Publication Date: 22.02.1979 International Filing Date: 20.07.1978
IPC:
H04Q 1/453 (2006.01)
H ELECTRICITY
04
ELECTRIC COMMUNICATION TECHNIQUE
Q
SELECTING
1
Details of selecting apparatus or arrangements
18
Electrical details
30
Signalling arrangements; Manipulation of signalling currents
44
using ac
444
with voice-band signalling frequencies
45
using multi-frequency signalling
453
in which m-out-of-n signalling frequencies are transmitted
Applicants:
Inventors:
Priority Data:
81911226.07.1977US
Title (EN) MULTIFREQUENCY SIGNAL RECEIVER
(FR) RECEPTEUR DE SIGNAL MULTIFREQUENCE
Abstract:
(EN) Detection of valid two-out-of-N multifrequency signals is realized by employing a microprocessor in conjunction with a controllably adjustable or settable reference threshold level (107) and a plurality of threshold detectors (104-1 through 104-N). Under control of the processor, a reference threshold level supplied to the detectors is set to a first prescribed level. Upon detection of a tone which exceeds the first threshold level the processor controllably sets the reference threshold level to a second prescribed level. Detection of two, and only two, tones which are present for at least a minimum prescribed interval are level. Detection of two, and only two, tones which are then considered valid.
(FR) La detection de deux signaux valables parmi N signaux multifrequence est effectuee en utilisant un microprocesseur conjointement a un niveau de seuil de reference (107) reglable de maniere controlee, et une pluralite de detecteurs a seuil (104-1 a 104-N). Sous la commande du processeur un niveau de seuil de reference fourni aux detecteurs est place a un premier niveau predetermine. Sur detection d"une tonalite depassant le premier niveau de seuil, le processeur place le niveau de seuil de reference, de maniere controlee, a un deuxieme niveau predetermine. La detection de deux, et seulement deux, tonalites presentes pendant au moins un intervalle minimum predetermine. Detection de deux, et seulement deux, tonalites qui sont alors consideres comme valables.
Designated States:
Publication Language: English (EN)
Filing Language: English (EN)