The TX-AVX is the ideal choice in installations where automatic switchover to an alternate video source is needed when the primary signal is lost. The unique power supply input allows the TX-AVX to be powered from a wide variety of existing ac or dc power sources. The TX-AVX has two video inputs and a single output. The detection circuit bridges the INPUT line. When a valid NTSC or PAL video signal is detected, the INPUT jack is connected to the OUTPUT jack. The output is designed to connect to a 75 ohm terminated load. In the absence of video input at the INPUT jack, the AUX INPUT jack is connected to the OUTPUT jack. The switching is accomplished by means of a high-quality RF relay. If power to the TX-AVX is interrupted, then the AUX INPUT jack is connected to the OUTPUT jack. The INPUT jack is 75 ohm terminated. The AUX INPUT is terminated when it is connected to the OUTPUT and is unterminated when it is not in use. Video detection is based on valid sync signals. The TX-AVX responds to valid NTSC or PAL sync while ignoring 50 Hz and 60 Hz hum and related induction artifacts. The TX-AVX is able to detect signals as weak as 0.5 V p-p. When a valid signal is detected, the relay connects the INPUT to the OUTPUT, and provides a ground connection to the SLAVE terminal, permitting the module to be connected as a video-present detector. Use in conjunction with RDL® BZR Alert Modules for convenient and reliable notification of status change.