PURPOSE: To obtain a terminal apparatus control device capable of transmitting the information of various content and executing fine operation control and monitor by identifying the content of information in accordance with a difference in the pulse width of an external operation control signal by a signal processing means.

CONSTITUTION: A terminal apparatus, i.e., an air conditioner 6 in this case, is provided with signal processing means 51 to 53 for identifying an external operation ON/OFF control signal sent from an interface 26 and other information signals by thier pulse width difference. On the side of the air conditioner 6, an operation control signal from a light receiving element 32 transmitted from an air conditioner interface 26 is branched and transmitted to a Shumitt trigger input buffer 53 through an input buffer 52 and a filter circuit 51. Here, temperature setting information based upon a high frequency pulse width modulation signal is outputted from the buffer 52. On the other hand, the high frequency component of the operation ON/OFF control signal is cut off by the filter 51 and outputted as an output (a') of the buffer 53. Consequently the temperature setting signal also can be transmitted to a part of apparatuses through the same control I/O terminal 8.