SoundCraft SM12 User Manual page 25

Rear Connectors
22
The connections to the rear connector panel are as follows:
INPUT (3 pin female XLR)
Pin 1 Ground
Pin 2 Signal (Hot)
Pin 3 Signal (Cold)
HI-Z INPUT, INSERT RETURN (1/4" 3-pole Jack)
Tip Signal (Hot)
Ring Signal (Cold)
Sleeve Ground
INSERT SEND, (1/4" 3-pole Jack)
Tip Signal (Hot)
Ring Signal (Cold)
Sleeve Ground
Input Module