Clear-Com MS-222 User Manual

INSTALLATION
/ Clear-Com MS-222
2-Channel Main
Station
2.2 CABLE CONSIDERATIONS:
The Clear-Com
intercom
line
is intended
to run on a
shielded twisted
pair
of cable per
channel
of intercom. One
conductor carries
full duplex ("two-way")
audio, the
other
conductor
carries the DC
power for remote
stations. The
shield is used
for ground
return
for audio and power.
When choosing interconnect
cable, keep the
following
considerations in mind:
1. DC resistance
of the ground or common conductor
affects crosstalk. For runs
longer
than 1 00
feet do not use
wire smaller than
20 gauge.
The total
resistance of the ground return
(the combined parallel sum of
all shields to a
location)
to any point in the system
should be under 1.5 ohms.
2. The capacitance
of the interconnect
cable affects system
frequency response and
side-tone
stability. Total
capacitance
should not be
greater than
0.25 uF
(capacitance
between
conductor and
shield) equivalent
to an intercom
system
containing
5000 feet of cable at 50 pF per foot.
PORTABLE INSTALLATION
CABLE
Typical
cable for
portable system
interconnections
is flexible, two-conductor,
shielded
microphone
cable.
For runs
less than 500
feet a cable
made of 24 gauge
wire is
acceptable.
For runs
longer than 500
feet use a 20
gauge cable or
larger.
Portable
remote stations such as belt-packs
have a pair of input and
output
connectors;
when installing
a system
that
includes
these,
they
can
be "daisy-chained"
or
"loop-thru" connected
along one
interconnect path.
Clear-Com provides
a one
input by three output Line-Splitter
(OP-1 00) that can also
simplify wiring. Daisy-
Chaining and
Line-Splitting
decreases
the amount of
cable required
and simplifies
the
installation.
PERMANENT
INSTALLATION
CABLE
Vinyl-jacketed shielded
pair is the cable of choice
for permanent installations.
Use a
low-capacitance
20 gauge wire for short
runs (under 500 feet) and
1 8 gauge cable for
runs
greater than 500 feet. Placing the
cable in conduit is recommended
but not
necessary.
Multi-pair cable
that is individually shielded
is acceptable for use in multi-channel
systems.
For cross-talk considerations
the shields
must be tied together
on both ends
of the cable to
produce the lowest possible
DC path for ground return.
11/90 Rev. 1.0
Page 11

Clear-Com MS-222 Specifications

General

Brand	Clear-Com
Model	MS-222
Category	Intercom System
Language	English