CATV Off-Air Signal Meter Module The XR-3 Cable Air module is used with the XR-3 modular test instrument base unit. The XR-3 Cable Air module is a signal level meter and analyzer for cable and terrestrial over-the-air broadcast TV installation and troubleshooting. It is ideal for CATV and UHF off-air antenna installers and private cable operators that need fast, easy signal measurements.