Cable converter for television signals with stereo audio signal

摘要

A cable converter for a television signal transmission having a stereo audio signal includes a coaxial output jack supplied with a 4.5 MHz aural intercarrier and a DC voltage for volume control and mute purposes. An interface circuit includes a pair of transistors connected in series for controlling the DC voltage level on the output jack as a function of desired volume level. One of the two transistors functions as a switch that may be operated from the cable head-end to provide a mute voltage level at the output jack for disabling the audio for nonauthorized channels. Optionally, a head-end control signal may operate another transistor for preventing coupling of the 4.5 Mhz aural intercarrier to the output jack.