Abstract: A telephone controller for connecting a single-line telephone in a local N-line system with other telephones equipped with similar controller comprises N interface units each connecting one telephone line to a dual conductor telephone bus in turn connected to the telephone.

Abstract: An automatic down rigger control system is disclosed for use with a down rigger trolling line operated by a motor for raising and lowering the trolling line. Via the motor, the control system automatically lowers an end of the trolling line to a predetermined depth point and automatically raises the end of the trolling line to a predetermined surface point. Also, a manual operation mode is provided for selectively raising and lowering the trolling line to a depth other than the surface point and predetermined depth point.

Abstract: An automatic trolling depth controller is disclosed for a fishing boat employing a downrigger system. A sonar depth indicating unit with a sonar transducer continuously measures changing depth as the boat trolls. A depth control unit is connected thereto which automatically raises and lowers the trolling line via a reversible motor in response to depth indicating signals of the depth indicator unit so as to automatically maintain the end of the trolling line at a substantially constant given spacing from the bottom despite variations in lake depth as the fishing boat trolls.

Abstract: A full wave DC to AC inverter having two SCR inverter switches which alternately conduct to connect a DC source across one section or the other of a center tapped power transformer primary to establish an alternating current in the secondary. A commutating circuit includes a single capacitor which is charged during the conduction of the inverter switches and is alternately connected to the conducting inverter switch to turn it off. The commutating circuit employs a single transformer which has a primary winding connected in series with the primary winding of the power transformer and a secondary winding connected through an SCR and to the capacitor. A pair of SCR's, which are gated on by commutation trigger circuits, control the discharge of the capacitor to the appropriate SCR inverter switch.

Abstract: A system for directing calls to selected parties on a multiparty line in exchanges equipped with selective multifrequency ringing generators is disclosed. Ringing applied to the line is converted to a DC logic level pulse train and is compared to logic level pulse trains generated for each frequency of the ringing generator. If the party represented by the frequency on the line has been manually selected for intercept and the pulse trains match for 250 milliseconds, the call is intercepted. Since the pulse trains are at logic level and are generated by the same ringing cycle, they are immune to phase shifts, voltage variations, and electrical noise.