The Dot Line Hot Shoe Photographic Slave Flash Unit is a slave flash unit with a hot shoe, designed for hot-shoe mount flash units on cameras. It also fits most flash accessory hot shoe mounts. This unit employs an optical triggering that requires no electrical connection to the camera. However, for this to work, there must be a master flash electrically connected to the camera. The slave attaches to the remote flash via the built-in hot shoe, senses the light from the master flash, and then triggers the remote flash to fire. The sensor cell must be positioned so that it can "see" direct or indirect light from the master flash.
The bottom of the slave has a female 1/4-20 thread to accept any tripod or ball joint head. The slave also features a standard accessory foot that can be used for mounting into a standard accessory shoe. The unit boasts a range of up to 60' (18.3 m) from the master flash. No batteries or external power are required, other than the light from the master flash.