PURPOSE: To improve the processing ability of a host device, by storing all the information from the host device, scanning it self-controllingly, reading, editing and displaying the required information from a storage section.

CONSTITUTION: All the information transmitted from a host device 1 via an output lead 2 is received at a reception section 4 of a display device 3 and stored in a memory of a μ-processor 5. The μ-processor 5 controls a key scanning circuit 9 periodically, reads information 10 from a display device 11, analyzes it and reads only required information from a built-in memory and edits it and transmits to a display device driving circuit 7. The circuit 7 transmits the received signal to a display 11 as display control information 8 such as current, and the information is displayed on a display element such as a lamp. Thus, the display is done independently of the host device 1, allowing to reduce the burden of the host device and to improve the processing ability.