TERMINAL ADAPTOR

PROBLEM TO BE SOLVED: To enable a terminal adaptor to handle an analog terminal in communication available state, even if a modular connector having provision for an analog terminal use communication port is plugged into a digital terminal use communication port by mistake. SOLUTION: This terminal adaptor TA has a changeover control circuit 6 that discriminates connection of a digital terminal to a corresponding digital terminal communication port P3, when a current detection circuit 5 detects a return current from an analog terminal or the digital terminal which receives an electric signal from an electric signal application circuit 4 and connects the digital terminal to a digital input output circuit 2 and that discriminates connection of the analog terminal to the corresponding digital terminal communication port P3, when the current detection circuit 5 detects no return current and connects the analog terminal to an analog input output circuit 1.