PURPOSE: To simplify the constitution of a terminal device which displays character graph information from an information center obtained via a subscriber telephone line on a television receiver for reading it, by using effectively a nonvolatile storage device in combination with a connecting switch.

CONSTITUTION: An input/output interface 12 is connected to a microprocessor 3 and the 1st and the 2nd input/output ports of the input/output interface 12 are grounded respectively via the connecting switches 13 and 14. The connecting switches 13, 14 decide whether or not an ID number and a key page in the nonvolatile are to be write protected depending on the connecting state. That is, in writing the ID number of the key page, when the connecting switch 13 or 14 is turned on, the ID number is stored in one storage area of the nonvolatile storage device 6, and the key page is stored in other storage area of the storage device 6. In this case, when the ID number is desired to be write protected, the connecting switch, e.g., is turned off.