Emulate pushed button in this circuit

Projects General Guidance
1

Hi mates.

How could I emulate a pushed button in this circuit? ... some kind of bridge and the a high from arduino?

Thanks

2

If you run the arduino and this device from a common ground, it would be possible to use a npn transistor with the the base attached to the trigger pin from the arduino, the collector attached to the lower voltage end of the switch and the emitted attached to the higher voltage end.

3

This seems to be a matrix keypad. If you just supply 5V or GND to it then you may damage arduino of the circuit. Maybe reed relays will work.