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4.3.02 REF IN Connector
4.3.03 OSC OUT Connector
4.3.04 STATUS LED
4.4 Rear Panel - 7124 RCU
4.4.01 Line Power Switch
4.4.02 Line Power Input Assembly
4.4.03 DIGITAL OUTPUT Connector
This is the general-purpose input connector for an external reference signal when
this is applied at the 7124 RCU as opposed to the main console.
NOTE: If the best possible phase accuracy at low external reference frequencies is
required, then a TTL reference signal should be applied to the rear panel
TTL REF IN input instead.
When external reference mode is selected the word LOCKED appears in highlighted
text along the top edge of the screen on the main console. Under unlock conditions
the word LOCKED flashes.
This is the output connector for the internal oscillator when this signal is to be output
at the 7124 RCU. Note that this output must be set active using the Oscillator Menu
on the main console in order to work.
This LED normally glows green when the 7214 RCU units is active. It blinks when
the main console is control signals to the RCU (such as when changing the AC gain
setting), which is useful for verifying that the fiber links are working.
Figure 4-7, Model 7124 RCU Rear Panel Layout
As shown in figure 4-7, the line power switch, line power voltage selector, digital
I/O port connector, power in/out connector, four fiber link connectors, and two BNC
signal connectors are mounted on the rear panel of the 7124 RCU. Brief descriptions
of these are given in the following text.
CAUTION: The model 7124 RCU may be damaged if the line voltage is set for
110 V AC operation and it is turned on with 220 V AC applied to the power input
connector. Please ensure that the line voltage selector is set to the correct line
voltage before switching on.
Press the end of the switch marked I to turn on the instrument's power, and the other
end marked O to turn it off.
This houses the line voltage selector and line input fuse. To check, and if necessary
change, the fuse or line voltage see the procedure in section 2.1.05.
This connector provides eight TTL lines, each of which on the 7124 RCU is a logic
Chapter 4, FRONT AND REAR PANELS
4-9
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