Racal Instruments 2461 User Manual page 42

2461Type C User Manual
Capabilities
Racal Instruments  1998
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Arming of the START and STOP circuits can be either internally
or externally derived. External arming is possible on all functions
except phase. The following arming modes are available:
Mode
1
2
3
4
5
6
7
8
9
The EXT ARM input can be from any of the VXI TTLO-7 lines,
or from the front panel ARM input.
For modes that use INT ARM, the STOP arming hold-off time is
adjustable for time interval measurements.
Correct use of the arming facilities can be used, for example, to
prevent premature triggering of the START and/or STOP circuits
due to external noise (e.g. contact bounce).
EXTERNAL FREQUENCY REFERENCE INPUT
The 2461 Type C can make measurements using as its
frequency reference an external signal connected to the front
panel port marked STD IN.
INTERNAL FREQUENCY REFERENCE OUTPUT
The frequency reference in use is available at the front panel
port marked STD OUT.
FREQUENCY STANDARD SELECTION
The user can select the reference from any of three sources to
Start
INT ARM
EXT ARM ↑
EXT ARM ↓
INT ARM EXT ARM ↑
INT ARM EXT ARM ↓
EXT ARM ↑ EXT ARM ↑
EXT ARM ↑ EXT ARM ↓
EXT ARM ↓ EXT ARM ↑
EXT ARM ↓ EXT ARM ↓
Theory of Operation 3-15
Stop
INT ARM
INT ARM
INT ARM