This circuit replaces the missing TICK signal for the system clock of the Amiga. If an Amiga mainboard is operated with a PC power supply, a jumper must be changed on this board. This ensures that the system clock (NOT the battery buffered clock) of the Amiga is controlled via the vertical blank signal. Disturbances in the image structure are not uncommon.
This small circuit generates from the power line frequency of 220Volt/50Hz a suitable TTL signal, which solves these errors and also makes the system clock run more accurately.
Please have a look at this picture that illustrates how to connect the TickIt circuit to your PSU. Additional information can be found in the Amiga Guide of the tickit.lha archive available on aminet.net.