Theory of Operation
4–2
ECO 422
The Primary and Backup signals enter through the BNCs. The signal goes
directly to the Relay where one switches through to the rear-panel Output and the
other terminates in 75
W
. The rest of the circuitry determines which signal goes
to the Output.
A copy of the Primary and Backup signals go to the Primary and Backup Check
circuitry. This block consists of a peak detector that compares the peak level of
the incoming signal with a predefined level from the Reference Voltage
Generator that is selected by the Voltage Selector. The result of this check is
ANDed with the results from the ten other input sets and sent to the Decision
Logic circuit that determines the state of the relays. Additional circuitry runs the
Alarm Driver for the remote output and the fault indicators on the front panel.
ECO 422 Detailed Circuit Description
Input and Comparators 2 through 7
The Input and Comparator circuit takes the input signals, selects between them,
and prepares the peak signals for the Decision Logic circuit. There are five input
signal sets on the Main board and six input signal sets on the Connector board.
All of the Input and Comparator circuits are identical for each signal set,
therefore only Channel 1 (on the Connector board) is discussed.
NEGATIVE
PEAK
DETECTOR
NEGATIVE
PEAK
DETECTOR
INPUT
BUFFER
INPUT
BUFFER
VREF
(P_AND)
(P_TEST1)
(B_AND)
(B_TEST1)
OUTPUT
PRIMARY
INPUT
BACKUP
INPUT
RELAY_DRIVER
Figure 4–2: Block Diagram of the Input Comparator
RF Relay.
The Primary input signal connects to 75
W
BNC, J17. The signal
passes through a 75
W
microstrip to the RF relay, K6. Meanwhile the Backup
signal enters J16 and connects to the other side of relay K6 also through a 75
W
microstrip. This relay switches the signal to either two 37.5
W
resistors in series
for 75
W
termination, or to the J18 output BNC. A 1.5 k
W
resistor (R262 for
Summary of Contents for ECO 422
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Page 14: ...General Safety Summary viii ECO 422 ...
Page 16: ...Service Safety Summary x ECO 422 ...
Page 17: ...Getting Started ...
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Page 31: ...Operating Basics ...
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Page 41: ...Operating Basics ECO 422 2 9 Figure 2 6 Setup for Adjusting R265 the User Level for SX 7 ...
Page 43: ...Specifications ...
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Page 63: ...Performance Verification ...
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Page 85: ...Adjustment Procedure ...
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Page 89: ...Maintenance ...
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Page 147: ... ECO 422 Changeover Unit FRONT PANEL 1 ...
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