Speck Electronics SSM - Manual (Page 24)

Chapter 3 Installation Section
The Expression Pedal Enable Switch on the front panel of the main
mixer must be depressed in order to operate the volume pedal.
The following chart represents the audio connections available at the 6
pin DIN connector at the rear of the SSM main unit.
PIN 1 - INSERT OUT-RIGHT
PIN 2 - INSERT OUT-LEFT
PIN 3 - COMMON
PIN 4 - INSERT IN-LEFT
PIN 5 - COMMON
PIN 6 - INSERT IN-RIGHT
Expression Pedal Enable Switch
Pedal Connector Pin
19