Clear-com SB-704 User Manual download pdf (Page 22)

SB-704 MAIN STATION

2-4

Figure 2-3: Fail Safe Power Distribution

The illustration above shows the proper power wiring of a system powered by

a single SB-704. The single-channel remote stations are connected to the ten

switched intercom connectors. These connectors derive their DC power

internally from the SB-704. The station comes set from the factory with the

power on the assigned lines #1 - #5 connected to channel A's power. The

power for channels #6 - #10 is sourced from channel B. Multiple-channel

remote stations are connected to the four intercom channels. In the case

above, a short on any one line will only take that channel down.

It is assumed that none of the power lines are interconnected in the external

system wiring. However, if a multiple-channel remote station that has not

been equipped for power line isolation is connected, those channels would

now have their power lines connected. The system will still work except that a

short circuit on any of the interconnected channels will cause both to fail thus

taking more of the system down with a single short circuit.

INTERCOM CABLE CONSIDERATIONS

The Clear-Com intercom line is intended to run on 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.

SB-704

RM-704

Remote

Station

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 41 42

No comments

Clear-com SB-704 User Manual Page 22