HP 5335A - Page 33

Operation and Programming
3-87. REAR PANEL FEATURES
3-88. A number of signal inputs and outputs are provided on the rear panel. TIME BASE OUT
provides a 10 MHz signal that may be used as a reference for other instruments. If the reference
to the HP 5335A is provided from another source, connect it to TIME BASE IN. This input
accepts either 5 or 10 MHz and internally multiplies it up to 10 MHz. Whenever a reference is
applied to the TIME BASE IN connector, the presence of that signal is sensed by internal circuitry,
and the HP5335A will automatically switch from the internal reference mode to the external
reference mode of operation. This switchover is indicated by the lighting of the EXT TIME
BASE annunciator on the front panel display. If the reference is removed, the EXT TIME
BASE annunciator will not automatically turn off. Pressing the RESET key will update the
status of the reference EXT TIME BASE annunciator. Do not connect TIME BASE IN to
OUT. No damage will occur but the reference frequency will be incorrect.
NOTE
Always press RESET after connecting or disconnecting a signal
to the TIME BASE IN. Do not connect or disconnect a signal to the
TIME BASE IN during measurements. FAIL 5.1 may occur, or the
measurement may give a false reading. If FAIL 5.1 does occur in
this situation, pressing RESET clears the condition.
3-89. TRIGGER LEVEL OUT provides A and B Channel DC trigger levels for display on
scopes. These are handy for a visual verification of proper triggering.
3-90. GATE OUT provides a low signal when the gate is open (see specifications). This can
be used in many cases as a visual indication of when the measurement occurs, or the
duration of the measurement.
3-91. The EXTERNAL ARM input can be used to specify the start and/or stop of a measurement.
The various modes of arming are determined by the two 3-position switches. Refer to
ARMING MODES, Figure 3-3.
3-17