This four-channel receiver is sold separately to expand the capabilities of the Calumet Four-channel Radio Flash Trigger Kit, which includes one receiver. It requires the Four-channel Radio Flash Transmitter (CF0050) for use.
The four-channel receiver comes with a standard 3.5mm jack, a 6.5mm
(1/4") photo jack adapter, and a PC flash socket. It can be mounted
with the included Velcro strap or by using the metal hook. The reciever
requires two AAA batteries (not included).