For making easier to adapt Light Pens/Guns from other systems or new ones, we added a 4 pins connector to the board. The connections are labeled in the board as VCC (+5V), TR (Trigger or D7), LS (Light Sensor) and GND.
Making the system compatible with [[Amstrad_Magnum_Phaser|Amstrad Magnum PasherPhaser]] games, the most accuracy light gun system for CPC.
==Counter/Timer Circuit==