Abstract: A portable transceiver and an ESN transfer system for a car telephone system. The ESN and the MSN, which are manufacturer-controlled numbers, are stored in an EEPROM mounted on the panel of the portable transceiver. When the panel on which the EEPROM is mounted is to be replaced, only the ESN is transferred to the EEPROM of the new panel. Upon completion of the ESN transfer, the ESN in the EEPROM of the replaced panel is rewritten to data, which would make its specific part, such as the manufacturer's ID number, to be judged "incorrect". No ESN whose specific part is "incorrect" can be transferred. The ESN transfer unit, connected to a connector provided in the casing of the portable transceiver, performs said ESN transfer.

Abstract: Speech signals appearing at the receiving and transmitting paths of a speakerphone which operates under voice switching, are received at a control circuit. The control circuit issues a control signal which assumes a first level in the event that a signal at the receiving path exceeds a signal at the transmitting path and which assumes a second level if the signal at the receiving path falls below the signal at the transmitting path. Communication loss is inserted in both the receiving and transmitting paths in response to the first level of the control signal, and is eliminated therefrom in response to the second level of the control signal.

Abstract: In a cellular mobile telephone system serving a plurality of cells, each of the cells being assigned a unique standby channel, the mobile station is assigned several standby channels and a system identifier identifying the system. The standby channels are scanned and one of the scanned channels having a highest signal level is selected. If there is a match between the system identifier of the selected standby channel and the system identifier of the mobile station, the mobile station is ready to originate or receive a call. If there is no originating or incoming call, the identifier of a call setup channel specified by the standby channel is stored into a different location of a memory. Otherwise, the identifiers stored in the memory are scanned, and one of the scanned call setup channels is selected.

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: 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 a 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: In a serial interface system wherein a master unit (26, 27) selects one or more of slave units (26, 27) as a destination by an identification number assigned to each slave unit and transmits a data signal to the destination in synchronism with a clock signal, a control path is added to a serial interface. When one of the slave units acts as a source either in transmitting data to the master unit or in transferring data to one or more of other slave units selected as a destination, the source activates the control path to activate, in turn, the master unit. When activated, the master unit sends a clock signal to the interface to make the source transmit or transfer the data in synchronism with the clock signal. Alternatively, the control path is dispensed with. In this event, the master unit is activated either by a command signal produced by the master unit or by a like command signal set forth from a source to the interface in response to an interrogation from the master unit.

Abstract: Waveform converting circuits are disclosed which eliminate errors in data reproduction due to the transitional response of low or high pass filters even if the data signal contains a D.C. component. The converting circuits have a comparator with first and second input terminals. The comparator produces a "1" or "0" output depending on the comparison of the voltages of input signals fed to these first and second input terminals. In one type of converting circuit, a low pass filter is connected between the signal input terminal and the second input terminal of the comparator, while the signal input terminal is directly connected to the first input terminal of the comparator. A feedback circuit including a low pass filter is connected between the output and the second input terminals of the comparator.

Abstract: A wave translating circuit includes a capacitor supplied with an input signal, a first resistor connected between a first potential point and the output of the capacitor, a second resistor connected between a second potential point and the output of the capacitor, and a limiter connected to the output of the capacitor.