LINEAR 108210 miniature transmitter The Model 108210 1-Channel Key Ring Transmitter is a miniature style transmitter designed for automatic door and gate operator applications. This transmitter is a single-channel device, pressing the pushbutton will send a signal to the receiver. The transmitter has a red test/operate indicator and is powered by a 12-volt battery. A molded-in hole in the case is for attaching the transmitter to a key ring. The Model 108210 is compatible with 310 MHz Stanley receivers and Model 109950, 302850, and 309013 receivers