See all articles from Syntax/Syntax ZX80 v4 n12
Aligned with the slot, you will find the pins correspond exactly to the ZX/TS pinout with three exceptions. RAM CS, ROM CS, and 9V are missing and the corresponding pins are empty. Pins outside the ZX/TS connector span perform 2068 functions—GND appears on 4 more pins (30 & 32, top & bottom) and +15V on pin 3.