ISP Technologies HDDS Master Control Module - Manual (Page 9)

Cat5 Connections
The figure below shows the connections for each output A, B and C of each zone.
Connections are done via standard Cat5 cables where pins 1 through 8 are connected
common to the same pins 1 through 8 at each end. As shown below two wires in the
Cable are use for balanced audio and 6 wires are used for power with two providing
ground and two for each of two 22VAC power signals fed down the cable.
Remote Level Control Connections
The figure below shows the connections used for the external Remote Zone Level
Control. The Master Control Module feeds 10VDC down a Cat5 cable are sets the zone
level based on the DC Voltage that appears on pin 5 of the Cat5 cable. The level
adjustment is done with an internal Voltage Controlled Amplifier VCA which means that
a simple DC voltage is used to set the remote level eliminating the need to feed low
level audio down a long run of cable.