Abstract: A telephone set control device. A dialing signal is converted into a pulse signal through a converter circuit; then, a pulse detection circuit generates a constant wavewidth signal to be coupled to a microprocessor unit, which then generates a signal, by means of the program instruction set in a read-only memory and A/D-latch circuits to operate a converter circuit to cut off the telephone connection at the end of a pre-programmed time period. The device enables the telephone owner to preselect the talking time and the number of digits to be dialed. The talking time and the number of digits which may be dialed are set in advance via a selective switch control means so as to let the user dial only the number of digits preselected and talk for only the period of time set; thereby saving time and preventing others from dialing unauthorized numbers.