The FM-27 board is the electronics of the FM-RL and FM-RLA receivers. It is made available for inclusion into studio equipment or remote vans. The board requires only three connections: Power 5-7 volts up to 500 ma. A speaker of 8-ohms. An FM antenna. The power and speaker are connected through the first four-pins of a ten-pin header. The receiver is switchable between main and subcarrier by grounding one connection on the board, which can be accomplished by placing a switch on the tone control. A six-pin header is provide for a dynamic noise reduction (DNR) expander or a 4-pole lowpass filter with the characteristics you specifiy.
The FM-27 board may also be manufactured for FM reception only. In FM operation, very narrow filters are available that make it possible to receive weak signals even when strong local stations are on adjacent channels.