Brake pressure sensor on master Cyl

I need to replace a leaky master cyl. on my 1977 450SLC.
Upon ordering I found that what is currently installed is not the
correct part.

This car calls for a brake master with a "brake pressure sensor" built
in.
Ordered the correct part and found the wiring for the fluid level
warning has been cut (easy fix) but the wiring for the sensor was
removed completely.

I'm sure i could rig it up if someone could tell me what the sensor
needs to be wired up to.
Any diagram or instruction would be most appreciated.

Thanks all,
Robert

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