Some of the original 406 MHz ELTs had split coaxial connections for the 121/243 MHz section and 406 MHz section of the ELTs. The connections interfaced to tri-band antennas with 2 connectors for the related frequencies as well. Therefore, manufacturers such Artex manufacture the C406-2 series ELTs with dual coax so that operators may still utilize their existing dual connector antennas.

More modern designs such as the C406-1 series combine all 3 frequencies into one coax connection. Compatible antennas have 1 coax connector as well. The 1 coax configuration is highly recommended and completely ideal for new installations.