The Model XT-4H 4-Channel Handheld Mid-range Transmitter is designed for use in various wireless remote control applications. When activated, the XT-4H portable transmitters will send a 2 watt, 27.255 MHz, digital encoded, FSK modulated, signal to their companion receiver. The receiver will verify the digital code, activate its output, and trigger the remote device. The Model XT-4H is a four-button, four channel transmitter. Each transmission is limited to a maximum of 30 seconds duration. The XT-4H portable transmitter is powered by two 9-volt alkaline batteries in series, supplying 18 volts. During transmissions, the red operation indicator will light (visible through a window next to the antenna). If the transmitter's battery voltage is low, the indicator will blink during transmissions. The XT-4H transmitter has battery supervision capabilities. If the combined battery voltage drops below 12 volts, a low battery message will be included with any signal transmitted, causing the receiver's low battery output to activate. The test button next to the indicator sends a test transmission when pressed. Two 8-position switches set the unit's system code. This code must be matched in the transmitter's companion receiver. There are 65,536 different system codes possible. The option switch selects the receiver's bank (for the XR-16 receiver only). Each transmitter is provided with a 6-inch rubber duck antenna and a removable belt clip.