Abstract: A 2-wire/3-wire converting apparatus having two transmission/reception terminals to be connected to a 2-wire circuit, a transmission terminal, a reception terminal and a common terminal to be connected to a 3-wire circuit. The converting apparatus includes an electric circuit for applying between the two transmission/reception terminals a voltage proportional to a voltage of a reception signal conveyed on the 3-wire circuit and appearing between the reception terminal and the common terminal and for applying a voltage between the transmission terminal and the common terminal a voltage proportional to a voltage obtained by subtracting the voltage proportional to the voltage of the reception signal from a voltage appearing between the two transmission/reception terminals.

Abstract: A battery voltage discriminator circuit for an apparatus having a battery and a plurality of loads which are driven by the battery and operate under various kinds of load conditions is disclosed. When the output voltage of said battery means drops under a predetermined reference voltage, the circuit generates a signal indicative of the voltage drop. The circuit has a reference voltage setting circuit for setting the reference voltage to one of predetermined values, which corresponds to the kind of the current load condition, and a reference voltage change circuit for activating the reference voltage setting circuit for a period of time in response to the change in the kind of current load condition.

Abstract: A data communication apparatus includes a data communication portion adapted to be connected to the public telephone line in parallel to a telephone set for data transmission/reception with another station through line connection, a termination command generating device for generating a termination command to terminate data communication by the data communication portion under predetermined conditions, a detecting device for detecting a termination command and generating a detection signal, a delay circuit for delaying the detection signal by a predetermined time, and a line connection terminating device responsive to the delayed detection signal for terminating line connection. There is a predetermined time margin defined by the delay circuit, during the time the termination command is generated until the line connection is terminated.

Abstract: A key input apparatus includes a light beam source, a plurality of input keys operable for varying the color of a light beam or intercepting a group or groups of light beams, an optical detector for detecting variations in the color of the light beam or interception of the group or groups of light beams, and a circuit for identifying operated keys based on outputs of the optical detector.