PURPOSE: To enable recognition of the transmitting capacity of a circuit at each point in time by comparing received data with prescribed transmission data and, if the action is normal for a fixed period, increasing the quantity of attenuation of the attenuator by a fixed quantity.
CONSTITUTION: A switching section 91 is actuated with a signal 21a, and transmission paths 50, 51 are by-passed with a transmission path 52, and transmitting and receiving terminals of a transmitting and receiving section 81 are connected through an attenuator 56. When the connection is in a state shown by broken lines, all the switching circuits 11∼13 select the receiving side. Predetermined data transmitted from a computer 21 passes through the attenuator 56 via a buffer 4, a transmission circuit 6, a transmitter 8 and an LED10 and transmit and receive data through a self loop that passes through a photodetector 9, a receiver 5 and a buffer 3, and test the action comparing the received data with prescribed transmission data. If the action is normal for a prescribed period of time, the transmitting capacity of the circuit can be known by increasing the quantity of attenuation of the attenuator by a fixed quantity.
FUSHIMI HITOSHI
YASUMOTO SEIICHI
OKADA MASAKAZU
