A ringing cadence filtering apparatus, which controllably prevents a subscriber device receiving ringing signals other than those having a prescribed cadence, is interposed betweeen a telephone line and a line device that has been assigned one of the telephone numbers of a multi-cadence service. It includes a controlled switching circuit through which a communication path between the telephone line and the line device connection port is normally interrupted. When a rining signal is present on the telephone line, whether or not the interruption is terminated and a path provided through the apparatus will depend upon whether the ringing cadence is that of the telephone number of the line device. To effect this determination, the telephone line input port is coupled to a plurality of ringing signal cadence detection circuits, each of which is responsive to a respectively different ringing cadence. However, only one of the cadence detection circuits has its output coupled to control the controlled switching circuit. To permit the subscriber line device to initiate an outgoing call, the apparatus includes an off-hook detector circuit, which causes the controlled switching circuit to establish a communication path from the telephone line connection port to the subscriber line device connection port in response to detecting an off-hook condition of the subscriber line device, in the absence of any other subscriber line device being connected with the telephone line.