Abstract: A frequency responsive selective ringing circuit detects a selected one of a plurality of frequency-distinctive ringing signals applied on either the tip or ring conductors of a telephone line, distinguishes between the respectively different frequencies on a rapid cycle-by-cycle basis, and either applies the ringing signal to telephone equipment to ring the telephone equipment if the ringing signal is one which is selected, or rectifies the ringing signal and applies the rectified DC signal to the ringing circuit of the telephone equipment. The rectified DC signal will not ring the telephone because the DC signal is not conducted through a capacitor in the ringing circuit of the telephone equipment.

Abstract: A selective ringing circuit for a telephone line includes a rectifier which is normally connected to the telephone line for rectifying the AC ringing and other signals. The rectified ringing signals will not activate the ringing circuit of the telephone equipment, because a capacitor in the ringing circuit is charged and will not pass current therethrough in response to the DC signal. The selective ringing circuit includes a switch-selective signal-detecting arrangement by which a predetermined one of the ringing signals is detected and is used as an activation signal, while the other ringing signals are rejected. The activation signal activates an electrical connecting device which, when activated, electrically bypasses the rectifier and directly electrically connects the predetermined selected ringing signal to the telephone equipment. An automatic number identification circuit includes a transistor switch which connects a predetermined ground resistance to the telephone line.