Alcatel Business Systems

Robert Girard

Andre Bonvallet

Raymond Blaszykowski

Daniel Perrein

Michel Canonne

Detector for telephone charging signalling in the form of periodic pulses derived from alternating current signals at specific frequencies transmitted in analog form by means of a line (2) comprising two wires (A, B), for example to a central office line interface circuit of a private telephone installation connected to an analog network subscriber line. The detector comprises an input filter (4) centered on the frequency (Ft) of the expected signalling, a sample and hold circuit (6) connected to the output of the input filter (4) and to the output of a clock (7) supplying a signal (HE) whose frequency (FE) is close to the value (Ft), a lowpass filter (8) within the band of which the characteristic signal from the sample and hold circuit is included, and a level detector (9) adapted to supply a presence signal for a characteristic signal at a level above a predetermined threshold at the output of the lowpass filter (8).

Telephone charging signalling detector suitable for central office line

A low-frequency alternating current signal detector for recognizing tone signals in a central office line interface circuit connecting a private telephone installation to an analog telephone network subscriber line. The low-frequency alternating current signal detector includes an amplifier (1) connected to the input of a bandpass filter (2) and to the input of a first rectifier-filter (3), a second rectifier-filter (4) and a threshold presence detector (5) connected to the output of the bandpass filter (2). The output of the threshold presence detector (5) selectively enables comparison by a comparator (6) of the bandpass filter input and output signals and signalling of the presence of an alternating current signal.

Low-frequency alternating current signal detector, in particular for

The invention concerns private telephone instalations, in particular key systems or small time-division switches, each provided with a central unit (2) including a time-division digital switching network (3) controlled by a control unit (4) to enable communication of a pluality of telephone or terminals (1) either directly by means of the switching network or by means of telephone lines (32) terminating at a local central office, the telephones or terminals or lines being connected to termination circuits (30, 31) which connect them to the switching network (3) via at least one time-division multiplex link (12) and to the control unit (4). A two-wire bidirectional signalling link (13) is time-shared between all the termination circuits for interchanges of signaling with the control unit (4); it is connected direct to a series-parallel converter circuit (8).

Private telephone installation architecture

Central office line interface circuit connecting a private telephone installation to a local central office. The central office line interface circuit includes a twin-loop line current polarity detector including a first optocoupler (57) for signalling polarity reversal, a transmission bridge (22) including a line loopback circuit operating via a second optocoupler (74) and provided with regulator and blocking means; it further comprises simplified tone and charging pulse detectors (24, 18).

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Colombes, France

Robert Girard