Abstract: An impedance matching cable system for electronically coupling a musical instrument to an amplifier. The musical instrument has at least one signal output conductor and a common conductor. A field effect transistor (FET) having gate, source and drain electrodes is connected to a bipolar direct current voltage supply having a pair of voltage end point connections and a center point voltage connection by connecting the source electrode to one of said voltage end point connections, and the current control device connecting the drain electrode to the other voltage end point connection. The center voltage connection point is connected to the common conductor and a coupler AC voltage at the drain electrode to the amplifier.

Abstract: A device is disclosed to prevent the unauthorized copying of magnetic tapes (tape "piracy"). The device utilizes an inaudible signal encoded into the tape program as the master recording is being made. A separate decoding circuit is to be installed in commercially available stereo tape decks. Whenever the encoded signal is present on the original recording, the decoding circuitry will short the bias signal of the tape deck being used to attempt to make the copies. This will prevent the deck from recording any of the program on the original tape.