Installation of cardrack, Power unit specs, central and station power – Ring Communications CB901EX User Manual
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CB901EX Operations Manual March 2011
cards). See Figure 1.10.
Connection of 24V power .
24 Volt is connected to the DP979 motherboard (PCB979) and to the power distribution board
(PCB935) in DP979/DP980. See figure 1.12.
Four self-healing fuses with red fail LEDs are used on each BF901 (6 stations on each fuse). The
red LED is lit when a short is detected in the power. The LED on the power distribution board is
normally green but turns red when any of the fuses on the BF901 detects a short. Only when the LED is
green is the Power Fail Relay activated. Contacts form C is available at terminal CN3.
INSTALLATION OF CARDRACK
When cable connections are completed, mount the rack to the backplate with the 2 pins. Two
magnets are fixed to the rear of the rack to hold it in closed position. Swivel the rack open to permit the
flat cables to be plugged into their relative pin-row positions on the rear of the motherboard. Take care
when folding the flat cable i.e., that they remain clear of motherboard pins when the central is closed.
POWER UNIT SPECS, CENTRAL AND STATION POWER
Although Ring-Master systems normally function on 24 VDC, power units shall be adjusted to 27
VDC which is the correct charging voltage when systems are connected to batteries for group/ all-call
or no-break battery back-up. Using 27 V also permits longer cabling from stations to central with a 3 V
tolerance to 24 V control voltage drop on longer cable runs. Ring-Master supplies a standard DC
power unit PSDC24V12A which is factory-adjusted to 27 V and can supply 12 Amp. It is adjustable .
A smaller power unit PSDC27V5A is also available for local use with remote stations, giving 5 Amp
DC, i.e., adequate for max. 20 stations. Power units can also be purchased locally provided that they
meet the specifications for supplying Ring-Master systems,- e.g., regulated, and with a max.
ripple/noise level of 30 mV peak to peak.
Note. The power unit should be equipped with over voltage protection.
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