RECEPTEUR MULTIFREQUENCE

L'INVENTION CONCERNE LES RECEPTEURS DE SIGNAUX MULTIFREQUENCES.DANS UN RECEPTEUR MULTIFREQUENCE, UN NIVEAU DE SEUIL VTH QUI EST APPLIQUE A UN GROUPE DE COMPARATEURS DE SEUIL 105-1 A 105-N EST REGLE PAR UN CIRCUIT DE GENERATION DE SEUIL VARIABLE 104 SOUS LA DEPENDANCE DES SIGNAUX MULTIFREQUENCES RECUS. LE NIVEAU DE SEUIL EST AUGMENTE RAPIDEMENT LORSQUE L'ENVELOPPE DU SIGNAL MULTIFREQUENCE RECU AUGMENTE ET IL EST DIMINUE BEAUCOUP PLUS LENTEMENT LORSQUE L'ENVELOPPE DU SIGNAL MULTIFREQUENCE DIMINUE.APPLICATION AUX RECEPTEURS DE SIGNALISATION DANS LES RESEAUX TELEPHONIQUES. In a multifrequency receiver, a threshold level (VTH) supplied to a group of threshold comparators (105-1 through 105-N) is controllably adjustable by a variable threshold generation circuit (104) in response to received multifrequency signals. As the envelope of the received multifrequency signal experiences a positive amplitude transition, the threshold level is increased at a fast rate (fast attack). Also, as the envelope of the received multifrequency signal exhibits a negative amplitude transition, the threshold level is decreased at a much slower rate (slow release).