Part III: Slot Machine Cheating · Electronic & Digital Cheating Methods

SCAM #30: Top-Bottom Joint / Circuit Completion Attack

How it works

The top-bottom joint is one of the oldest slot cheating devices, consisting of two parts: a “top” (a metal rod bent into a hook or “q” shape) and a “bottom” (a long wire, typically guitar string). The bottom wire is inserted through the coin chute up to the circuit board, making contact with the hopper control circuit. The top piece is inserted into the coin slot. Together, they complete an electrical circuit that triggers the coin hopper to dispense continuously. This attack exploits the machine’s own electrical systems by providing an alternate path for electricity to flow, effectively “hot-wiring” the hopper. Variants were developed for different machine models, with approximately 50 different wire configurations created to match specific machine internals. The device worked because early electronic slot machines had inadequate circuit protection.

Where it appears

Early electronic slot machines (1970s-1980s) with electromechanical hoppers and insufficient circuit isolation — Bally, IGT, and other manufacturers

On the record

The top-bottom joint was popular in the 1970s and 1980s. Tommy Glenn Carmichael learned the technique in 1980 and used it successfully for years until improved security rendered it obsolete. He received a 5-year prison sentence (served reduced time) for using the device. The technique inspired Carmichael’s later, more sophisticated inventions.

Published as a detection reference for surveillance, compliance and gaming-operations professionals. Thresholds and tuning are set by the property. Nothing here is instruction — the method is described so it can be recognised.