Consisting of a micro controller board and two small connection boards, this system prevents the special solenoids from locking on and causing damage to the driver board. Suitable for Williams system 3 - 11b and Data East non-reflexive (-01 and -02) MPU / driver boards. Effectively works by intercepting the signals from the special solenoid switches (SST).  When one of these is activated, the controller board will output only a pulse for driving the solenoid (SSD). Normally, the solenoid is energised as long as the switch is active, and if the switch gets stuck on, then so does the solenoid!

The boards are connected by three 8P8C RJ45 ethernet cables, which are not included as it depends where the controller is mounted as to what length they should be.

More information can be found here by the designer.

https://pinside.com/pinball/forum/topic/dumbass-test-and-reproduction-pcbs/page/27#post-7644242