Interfacing the interface....
To drive the landing gear indicator and the unlock warning lamp, some reed relais and optocouplers are necessary. The simkits interface is able to drive only LEDs but I need 24 Volts for most of the original parts.
But this one was easy. The indicator has three wires, one common, one for "up" and one for "down". You just have to connect the 24 Volts to one of them and the corresponding sign will show up. If there is no signal at all... it shows the well known stripes.
The lamp socket has also three terminals. A common, a signal and one for the "push to test". You can push the red cap and the light will go on to test the bulb inside.
That's the good side of this old technology, everything is built simple and reliable.