A transmission relay circuit, a broadcast signal relay method, and a signal detection device are disclosed. Preferably, the transmission relay circuit includes a microcontroller, a broadcast signal sensing and discerning circuit configured for determining the broadcast signal selected from a group consisting of (NTSC, ASI, DS-3, SDI, and HD-SDI signals). The method preferably includes the steps of determining a signal type, directing the signal to an analog broadcast signal processing circuit when the signal is determined to be to be an analog video signal, directing the signal to a digital broadcast signal processing circuit when the signal is either a digital video signal, or a digital video transport signal, and relaying the processed signal to a local loop provider. The detection device preferably includes at least a multi-layer printed circuit board with an isolation/buffer amplifier and terminator, and a signal detection circuit for detecting and determining the broadcast signal type.