Speck Electronics SSM - Manual (Page 56)

Chapter 4 Operation Section
This multipin connector will accommodate any of the Model SSM
Expanders for a potential of 56 inputs (28 stereo channels). For the
proper pin out configuration and installation instructions, refer to the
Interface Section of this manual.
This 9 pin circular connector will accommodate the connector from the
power supply cable. The connectors are keyed so they will only fit in
one direction. For installation instructions refer to the Interface Section
of this manual.
This grounding terminal should be used when it is necessary to connect
the Model SSM to a qualified ground. This terminal is internally
connected directly to the metal chassis of the SSM and does not connect
to the DC power supply common or audio grounds.
Refer to Figure 11 for location of items 27 and 29.
27. Expander Connector
28. Power Supply Connector
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29. Ground Terminal