This four-channel transmitter is sold separately to expand the capabilities of the Calumet Four-channel Radio Flash Trigger Kit, which includes one transmitter. It requires the Four-channel Radio Flash Receiver (CF0051) for use.
The four-channel transmitter has a hot-shoe for on-camera mounting and
is powered by a 23A, 12-volt battery, which is included. It's large
digital read-out specifies which channel is selected. The transmitter also has a socket for and optional pc cord connection.
Instructions are provided.