Adding the expansion lid to Maxon’s SD-125EL RF link module provides the benefit ofinstalling CTCSS modules, modem boards, or other option boards. Take a look andsee how they can extend your communication possibilities Installing the(optional) Maxon CTCSS Encoder / Decoder (SD-010) for the SD-125E SeriesIncreases privacy during audio applications and operates on all 38 EIA standardCTCSS tones.