Abstract: 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).

Abstract: Electronic telephone set, comprising a transmission circuit arranged for being coupled to a telecommunication network and for receiving and transmitting speech signals, a keyboard means comprising a first matrix with respective numbers of intersecting first and second conductors and at the intersections of the first and second conductors key switches coupled to the respective first and second conductors for producing dial information and status information and including a second matrix with one intersecting first and second conductor or a plurality thereof respectively, and having setting circuits conducting current in one and the same direction coupled to the respective first and second conductors at selected intersections of the latter first and second conductors, whereas all second conductors of the second matrix are arranged common to those of the first matrix, and including a control circuit arranged for generating dialling signals compatible with the telecommunication network in response to the dialling

Abstract: An arrangement that enables an adjunct processor to determine the service status of switching system communication ports to which the adjunct processor is connected, without reliance on switch-to-adjunct status-conveying messages. In-service and idle ones of the ports participate in calls on a rotating basis. Following receipt of N calls, where N is the number of in-service ports connected to the adjunct processor, the arrangement determines whether each port that is presently designated as being in-service and idle has participated in one communication before a port has participated in a second communication. The arrangement then treats as out-of-service any port presently designated as being in-service that has been so determined a predetermined number of sequential times. It also selectively designates as in-service ports that have participated in communications since the last determination had been made.

Abstract: An audio compression system wherein the compression theshold may be adjusted to a calibrated level. The audio compression system is utilizable in a receiver system whereinan audio input signal received by the receiver system via a communications channel is applied to conditioning circuitry. The conditioning circuitry, in turn, provides a conditioned input signal to an acoustic transducer element for generating a corresponding audio output signal. The audio compression system compares the conditioned input signal and an initial threshold signal to provide a comparator output signal corresponding to the difference between the conditoned input signal and the initial threshold signal. The comparator output signal is provided as a control input to the conditioning circuitry. If the conditioned input signal exceeds the initial threshold signal for a preselected period of time, then the initial threshold signal is switched to a second threshold signal.

Abstract: In order to perform voice-switched telephoning, a hands-free telephone includes a speaker, a microphone, a receive variable attenuator (R-ATT), a transmit variable attenuator (T-ATT), a receive signal detector, a transmit signal detector and an attenuation control circuit. The telephone also includes an auxiliary control circuit which prevents the output of the transmit signal detector from reaching the attenuation control circuit during a transient period between a call origination and the beginning of conversation. During the transient period, only the speaker is enabled to output a ringback tone therethrough. When the output level of the transmit signal detector exceeds a predetermined level, the auxiliary control circuit passes the output of the transmit signal detector to the attenuation control circuit to start the voice-switched telephoning. Once the auxiliary control circuit passes the output of the transmit signal detector, it holds this state until the conversation finishes.

Abstract: A remote coverage system extends the effective coverage area of a cellular mobile radiotelecommunications (CMR) master cell. When a mobile unit assigned to the master cell moves from the master cell's coverage area into the coverage area of a satellite cell, the satellite cell sends a signal asking for a handoff of the mobile unit to it. When the handoff occurs, the MTSO exchanges signals with the mobile unit via a relay unit located at the master cell site. The relay unit relays signals between the MTSO and the satellite cell.