This is a standard mechanical tow hook with compressive spring. It has 4 settings screws for different rudder deflections: circle tow, forward tow, accelerate and glide. Screws are made from stainless steel and coated by teflon tape to prevent unwanted slew. Different springs for unlatch tension from 3 to 9 kg are possible.
I make version for mechanical timer and version for electronic timer, ready for two micro-switches. The front switch detects hook in the forward position. The back switch detects the moment when the hook is unlatched.