ADC RF Worx, Руководство пользователя

Страница: 9 / 26

ADCP-61-810 • Issue 4 • September 2004
Page 3
© 2004, ADC Telecommunications, Inc.
After successfully switching to the backup amplifier, input power to the Primary amplifier is
turned off.
A single failure condition is indicated on the front panel of the RDS and through the SWatch
monitoring software. In addition, a single failure condition causes the RDS to close the
Normally Open (NO) alarm relay contacts on the rear panel.
Figure 2. Block Diagram for Redundant Amplifier Mode Operation
If, in a single failure condition the backup amplifier gain also fails, a “dual failure condition” is
indicated on the front panel of the RDS and through the SWatch monitoring software. In such a
condition, the alarm contacts are already closed from the single failure that preceded the dual
failure. The alarm contacts remain closed in the dual failure condition.
2.1.1.1 Assured Best Failure (Redundant Amplifier Mode)
When the RDS goes into a dual failure state, the assured best failure algorithm of the
microprocessor will momentarily compare the gain of the A & B side amplifiers. It will then
choose the amplifier with the strongest gain and “lock” onto it until the dual failure status
condition is cleared. This assures that the RDS uses the best possible amplifier during a dual
failure condition—to minimize service degradation/interruption.
2.1.2 Dual A/B Switch Mode
The RDS can also function as an electronic A/B switch as shown in Figure 3 . This mode is used
to provide redundancy to amplifiers or receivers used anywhere in the forward path of the cable
television network.
Note: Loss of signal status, defined as a loss of input RF signal to the RDS, also causes an
alarm contact closure. In this case, the failure is in the network upstream of the RDS. Loss
of signal status is also indicated on the LOSS OF INPUT LED on the front panel of the
RDS and through the SWatch monitoring software.
RF OUTPUT RF INPUT RF
RDS-1 A A
B B
RF
A INPUT
POWER
POWER
PORT 1 PORT 2
MICROPROCESSOR
CONTROL
PRIMARY
AMP
COMPUTER
MONITOR &
ALARM
SYSTEM
B INPUT
A OUTPUT
B OUTPUT
STANDBY
AMP
10141-A