How to Read Relay State using Digital Pin?


hi everyone, having trouble reading value here in setup:

there 2 arduino uno rev3 units:

setup:
*ard2
- has 12v relay card connected control warning light (on/off) if conditions are            met (such if condition satisfied, ard2 send signal pin 7 pass relay card activate warning light).

*ard1
- located in location, needs read state of relay1 only(in relay card) , not pin 7 . ard1 use digital pin 8 (as input) read state of relay1 (if triggered or not, 0 or 1)

problem is, don't know in relay card connect ard1's digital pin 8 & reference ground reading, please me . can use dry contact port of relay card?

below setup diagram .

as read it, want confirm light receiving voltage battery.

i presume have pair of wires between 2 arduinos.

simply use opto connected lamp such lit when lamp lit. output acts switch monitoring arduino.

weedpharma


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