Clear-Com MS-704 - Manual (Page 22)

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 S T A T I O N S 2 - 6
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 RS-601 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.