Trane Engineered Smoke Control System Application Manual page 85

Checking outputs
3. Set the multi-meter to measure Vdc, then measure the voltage across
the analog output at the signal and common screw terminals.
The measured voltage should be less than 0.1 Vdc. If the voltage is
greater than this, a shared power supply may be incorrectly con-
nected. Check along the wire to make sure that no additional connec-
tions have been made.
BAS-APG001-EN 73