Carrier-current selector supervisory equipment

The rapid advances made in the application of automatic principles to the control of electrical energy have produced many new and novel installations. This paper describes a supervisory system which centralizes the control and indication of all power used in operating a modern interurban railroad. Supervision is accomplished over a single circuit consisting of one insulated wire with ground return. A single frequency carrier current is used for transmitting all signals over the circuit connecting all stations. Considerable attention has been given to make the equipment simple in design, rugged in construction, easy to install and convenient to maintain.