Abstract: In a system for detecting an angle of a joint coupled through a reduction mechanism to a drive motor, an absolute type rotation angle detector and an incremental-type rotation number detector are coupled to the motor for detecting the rotational angle and the rotation number of the motor, respectively. The detected rotational angle and the detected rotation number are used to calculate the rotational angle of the joint. The incremental-type rotation number detector is provided with a battery for energization during interruption of a power supply.

Abstract: A lamp circuit is provided having a constant current type AC power source and a plurality of isolation transformers connected in series with the AC power source. The secondary circuit of each isolation transformer is connected to an electric lamp. The voltage-time area, which is measured from the rise of the voltage output signal of the power source to the rise of the current output signal of the power source is detected and is compared with a reference predetermined value. Thereby when the detected value exceeds the reference value an alarm signal is generated and the number of the disconnected lamps can be determined and displayed.

Abstract: In an inverter apparatus of the type comprising a plurality of thyristors connected between a DC source and an AC load, a control circuit for sequentially turning ON and OFF the thyristors according to a predetermined sequence, and a reverse bias circuit including a pair of power transistors respectively connected in series with the DC source and ON.sup.. OFF controlled by the control circuit for applying a reverse bias to the thyristors to effect simultaneous commutation thereof, and a pair of diodes connected across the DC source, there are provided a second thyristor connected between the plurality of thyristors and the power transistors and turned ON at the time of commutation of the plurality of thyristors by the control circuit and a reactor connected in parallel with the second thyristor.