Specifications

Reference Guide
3-13
System Installation System Power and Ground Connections
3.6 System Power and Ground Connections
After installing the system power cards into the chassis, make the power and ground
connections to the chassis as described in this section. Each chassis has a terminal block for
the DC voltage, ringing generator, and ground connections.
3.6.1 Front-Loading Chassis with Power Supplies on the Side (891630)
Figure 3-8 shows the power and ground connections to a front-loading chassis with power
supplies on the side.
Connect the grounds and DC power signals to this terminal block by inserting the wires (max.
14 gauge wire) in the proper slots, then tightening the screws adjacent to the slots to secure
the connections. For safety reasons, no more than one-eighth inch (0.125") of each connecting
wire should be exposed.
No uninsulated wire should be visible from the terminal block.
The power terminal block also provides dual power connections at
V
A
and
V
B
where
redundant power feeds are required. The
V
A
pins feed power supply slot S1, and the
V
B
pins
feed power supply slot S2.
In addition, you can connect the
V
N
pins of the block to an external -48V source for powering
voice cards and their circuits. The
COM
(common) pin is the systems digital ground
connection, and the
RGR
(ringer) pin is for connecting an external 20 Hz ring generator input
to the chassis. The ringing voltage bias is selected by a connection to
V
N
+
or
V
N
-
.
When operating from a DC source, a protective earth ground must be connected to the
“Protective Earth/Chassis Ground” (
) terminal block location. When operating from an
AC source, this connection is made through the power cords “third wire” ground.
If your system will be connected to voice circuits that use E&M or FX ground-start signaling,
connect the chassis ground terminal to the same chassis ground used by the external PBX or
other system. Tying the chassis grounds together will ensure proper signaling operation and
transmission between the two ends of each circuit.
Note:
If -48 VDC is applied to V
A
or V
B
. DO NOT connect external power to V
N
.