An external genlock for the Amiga which connects to the RGB port. It has 2 x composite inputs, 1 x SVHS input, and an RGB composite with SVHS output. The G-Lock is also capable of mixing sound with 2 mono inputs and a single output.
BOM details from internal GVP documents can be found here: https://archive.org/details/gvp-bom-genlock-ntsc