Clear-Com PTX3-21 - Wireless IFB Transmitter (Block 21 / 538-563 MHz)The PTX 3 adds DSP capability and a convenient LCD interface to this IFB transmitter, with the same physical size and interface capabilities. The PTX 3 also offers selectable LF roll off and compatibility with other brands. Features: Operate between 486. 4 and 639. 9MHz Stand alone or rack mountable with the PRK 2 kit Selectable Low Frequency roll off Locked setting prevents accidental changes Overcomes channel noise and compandor artifacts Tough