Extended Range Direct Mode
Extended Range Direct Mode (ERDM) is a radio and repeater feature that allows repeater operation on simplex.
The repeater receives the radio transmission on slot 1 and (re)transmits this on slot 2. Similarly, the radios all receive on slot 2 and transmit on slot 1. The transmit and receive frequency is the same. The advantage of this is that it permits repeater-like coverage but without the need for obtaining a repeater licence.
Customers need to clarify this with their telecommunications regulator, as installing an ERDM repeater can extend the coverage of their simplex channel beyond the area they are licences for.
ERDM is supported in all SLR repeaters. In order to use a single antenna for transmit and receive, a high speed antenna switch is needed. The (electromechanical) antenna relay, normally sold with the MTR3000, cannot be used for this. There is a high spped witch available for th SLR1000 but a 3rd party switch would be needed for the SLR5500 and SLR8000.