Clear-Com RM-704 - Manual (Page 24)

M S - 7 0 4 / R M - 7 0 4 F O U R - C H A N N E L M A I N / R E M O T E 2 - 6
is affected by blinking the red short light(s) corresponding to these channel(s).
This light will assist in locating the shorted or overloaded channel. Shorts are
generally caused by miswiring or damaged cables. Overloads are generally
caused by connecting too many beltpacks and stations to a channel.
The current requirements of Clear-Com remote stations and beltpacks vary
with model and use. A station that is simply on and idling in the circuit may
draw only a small amount of current.
The MS-704 provides DC power to operate Clear-Com beltpacks and remote
stations. The power is distributed between the four channels and will support
up to 40 1-Channel Beltpacks or 10 speaker stations or 12 headset stations.
INTERCOM CABLE CONSIDERATIONS
The Clear-Com intercom line is intended to run on a shielded pair cable. One
conductor carries 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 500 ft. (152.5 m) do not use wire smaller than 20 gauge.
2. The capacitance of the interconnect cable affects system frequency
response and sidetone stability. Total capacitance should not be greater
than 0.25 uF.
PORTABLE INSTALLATION CABLE
Practical cable for portable system interconnections is flexible,
two-conductor, shielded microphone cable. We suggest you use BELDEN
#1800F (24 gauge). For runs longer than 500 ft. (152.5 m) use a 20 gauge
cable or larger (BELDEN #8412).
PERMANENT INSTALLATION CABLE
Vinyl-jacketed shielded pair is the cable of choice for permanent installations.
Use a low-capacitance 20 gauge wire for runs under 500 ft. (152.5 m). We
suggest you use BELDEN #8762. For runs longer than 500 ft. (152.5 m), use
an 18 gauge cable (BELDEN #8760). 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.
WIRING DIAGRAM
The diagram shows using a multi-pair cable to connect two stations. Note that
the power and shield wires of each channel are not connected together.