That’s it on the left, next to a standard MIDI cable plug. The whole thing is so small it fits inside a MIDI plug and can run off the power supplied by the MIDI output, driving a small pizeo buzzer.

A bunch of pads connected to a MIDI out port is as old an idea as the Akai ... each having their own PS/2 output. A few ribbon cable to 8-pin header adapters were manufactured, and the entire ...