PURPOSE: To improve the execution performance on the design aspect by obviating the need of the secret operation by inputting a cipher No. and releasing the electrical lock by repetitively operating the calling-out button of a door phone subsidiary device.

CONSTITUTION: When the calling-out button 100a of a door phone subsidiary device 100 is continuously operated for a prescribed selection time or more, the selective set to the electrical lock control mode is performed by a mode selecting part 12. Each time when the operation interval of the calling-out button 100a exceeds a prescribed time, during the electrical control mode period, a signal processing part 10 sends out a discrimination signal to the door phone subsidiary device 100 side from a discrimination signal transmission circuit 13, and digit division is carried out, and decoding is performed, having the number of times of operation of the calling-out button 100a in each divided digit, as cipher No. Further, the decoded cipher Np. is compared with the cipher No. which is previously set in a cipher No. setting part 14, and if accordance is judged, a lock release control signal is transmitted to an electrical lock 500 from an electrical lock control part 17, and lock is released. Accordingly, the need of a secret operating device can be obviated.