Abstract: A control system for use in a conventional telecommunications system comprising a common telephone line to which plural telephones may be connected. The line is arranged to carry plural series of electrical ring-initiating signals, each for a respective one of plural telephone numbers serviced by the line. The control system comprises plural controllable ports and a controller. Each of the ports is associated with a respective one of the series of ring-initiating signals and is arranged to have a telephone and/or some auxiliary device, e.g., FAX machine, answering machine, computer, etc., connected thereto. The controller is coupled to the line and the controllable ports and detects an analyzes each of the plural ring-initiating signals on the line and also monitors the status of the line, e.g., if there is a "busy signal", an "on-hook signal", an "off-hook signal", or other signal on it. Depending upon line conditions the system controls the ports to which the telephones or other devices are connected, e.g.