Abstract: A variable resistor including a resistive element and a conductive element supported by a plate. Contacting terminals are provided on one or more ends of each element. A carriage is slidably supported above the elements and a conductive roller is supported from the carriage by a suspension member that biases the conductive roller against the elements. The effective length of the current path through the resistive element is varied by using the conductive roller to electrically connect the two elements to one another along different portions of their length. In a preferred embodiment, the carriage moves under the guidance of at least one guide bar and the conductive roller is suspended from the carriage by a coiled spring.

Abstract: A sync crosstalk cancelling circuit features a record/playback head, capable of sync recording, molded in one piece with a record head section and playback head section and another record/playback head identically constructed. The recording head section of the record/playback heads are either connected in series or parallel at the same polarity, with the same recording current applied to both recording head sections, and at the same time, playback signals reverse in polarity to each other are obtained from the playback head sections of the record/playback heads, their gains adjusted and then applied to a mixing circuit. The mixing circuit outputs the playback signal with the crosstalk elements cancelled.

Abstract: A variable resistor includes strip-shaped conductive and resistive elements on an insulator plate. A cylindrical-shaped, conductive roller element can be rolled over the conductive and resistive elements to vary resistance. Thereby, substantially all sliding movement or contact is eliminated, which eliminates noise and prevents excessive wear.