Sekonic Transmitter Module RT-EL/PX for L-858D-U Speedmaster light meter. Used to trigger Elinchrom(Skyport) and Phottix (Strato) enabled lighting and receivers. When used with Elinchrom provides Triggering and controlling the power level of the light Triggering and controlling the power level of modeling lamp with ON/OFF When used with Phottix Selecting the groups and triggering a flash for measurement requires using a Phottix® Indra, Mitros+ set for StratoTM II reception or flash attached to Phottix® receiver with StratoTM II protocol.