Tektronix ECO422D Instruction Manual page 91

Performance Verification
Press the Reset button on the front panel and try to return the signal source
to Primary.
CHECK - - that the Primary signal still shows an error and automatically
switches back to Backup. If the ECO422D does not continue to show the
Primary signal in error after the reset, continue adding attenuation until the
Primary signal switches to Backup again.
CHECK - - that the ECO switches between 2 and 4 dB down.
14. Serial Digital Audio Check for Channel 1 Backup
Switch between 2 and 4 dB down from nominal
Connect the equipment as shown in Figure 5- -4 except swap the Primary and
Backup cables so that the attenuator is on the Backup side.
Set the Channel Configuration switches to Disabled (Signal not checked) for
all channels. (set all the DIP switches on S1 through S11 to "open").
Set the Channel Configuration switch to Serial Digital Audio for Channel 1
(set S1- -5 to "closed," S1- -1 through S1- -4 "open," and S1- -6 through S1- -8
"open").
Set the step attenuator to 0 dB of attenuation.
Set the TG700 AG7 to output either a 1000 or 800 Hz serial digital audio
tone on channels 1+2 and 3+4.
Press Reset.
CHECK - - that there are no errors shown for either the Primary or Backup
ECO422D sync sources.
Set the ECO422D to "Backup" Sync Source and Auto Switch to "Switch on
Fault."
Add attenuation, 0.5 dB at a time, to the Backup input signal until the signal
source switches to Primary.
Press the Reset button on the front panel and try to return the signal source
to Backup.
CHECK - - that the Backup signal still shows an error and automatically
switches back to Primary. If the ECO422D does not continue to show the
Backup signal in error after the reset, continue adding attenuation until the
Backup signal switches to Primary again.
CHECK - - that the ECO switches between 2 and 4 dB down.
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ECO422D SD/HD Changeover Unit Instruction Manual