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Operation and Reference
11. Ext Ref (ndicatof: The Ext Ref Indicator illuminates
if an external reference or option 001 (internal
10 MHz oven reference) is connected to the
rear-panel Ref In connector. The indicator flashes
if the internal oscillator is not phase-locked to the
external reference.
12. Modulation Indicators: The modulation indicators
.iiiuminate if amplitude or phase modulation
is enabled.
13. Main Function key group: These keys select
the main signal output function or dc-oniy.
14. [Amptd Cal] key; This key calibrates the amplitude
and offset of the output signal. When preceded by
the [Shift] key, It initiates an instrument self test.
15. Sync Out: A square wave synchronized output
signal is available at this connector and rear-panel
Fast Sync connector. This signal Is synchronized
with the output signal crossover point (zero volts or
dc offset voltage). The front-panel sync output
functions for frequencies beiow21 MHz.
Caution
The maximum peak voltage that can be safely
applied between chassis and outer conductor of
any of the HP 3325B input or output signal
connectors is ±42V.
16. Aux 21-60 MHz Rear indicator: This indicator
illuminates when the rear-panel Aux output is active.
17. [Rear Only] key: In standard instruments, this key
switches the signal output from front-panel to
rear-panel. The rear-panel output is active when the
adjacent indicator illuminates. In instruments with the
high voltage option (002), this key switches from
norma! to high voltage output. The adjacent indicator
illuminates when the high voltage output is enabled.
The key is labeled "40 Vpp, 40 mA, 0-1 MHz" for
option 002. In option 002 instruments, no rear-panel
signal output is provided.
18. Main Signal output: Standard output impedance is
500. High voltage output option 002 output
impedance is nominally < 1Q at dc and < 10O at
1 MHz. Load impedance must be at least 5000.
Standard and high-voltage outputs are
fuse-protected.
If the standard instrument signal output is not
terminated by an external 50Q load, undesirable
distortion may result, particularly at higher
frequencies. Similar conditions may result if frie
high voltage output (option 002) is terminated by
less than 500P.
19. Modulation Source key group: These keys select
the modulation signal function.
20. [Instr Preset] key: This key restores the HP 3325B
to a predefined state (see table 1-1). When preceded
by the [Shift] key, Instr Preset clears the discrete
frequency sweep segments from memory.
21. Circuit Breaker Reset Button: Disconnects power
supply from power line when the iine voitage
exceeds upper limit. See the Installation Manual for
information on resetting the breaker and voltage
limits,
22. Voltage selection vs fuse used: This module
contains the line fuse and configures the HP 3325B
for local iine voltages. Refer to the HP 3325B
Installation Manual for line fuse selection and iine
voltage configuration.
23. Mode/RS-232 switch; These switches enable the
HP 3325B enhancements, turn-on configuration, and
RS-232 characteristics.
24. HP-lB/RS-232 connectors: Remote control of the
HP 3325B by an external controller is accomplished
through these connectors.
25. Fan Filter: See "Instrument Cooling" in the
Installation Manual for information concerning the
fan and its filter.
26. Phase Mod In: Input connector for a phase
modulating signal of ±5V maximum peak voltage.
27. Mod Source Out: Output connector for the internal
modulation source.
28. Amptd Mod In; Input connector for an amplitude
modulating signal of ±5V maximum peak voltage,
• 29. Main Signal Out: The output signal is switched to
this connector by the front-panel [Rear Only] key.
instruments with the high voltage option 002 cannot
switch the main signal to the rear-panel connector.
30. Fast Sync; A square wave synchronizing output
signal is available at this connector. This signal is
synchronized to (changes state at) the output signal
crossover point (zero volts or dc offset voltage) and
operates from 0 to 60 MHZ.
31. Ref Out: A 1 MHz signal from the HP 3325B
reference circuits is available at this connector.
32. Aux 0 dBm: A signal is available at this output for
frequencies between 19 MHz and
59 999 999.999 Hz.
33. Ext Ref In: This external frequency reference may be
used to phase-lock the internal 30 MHz oscillator.
34. 2-Blank: A TTL-compatible output is present during
a sweep operation.
35. X-Drive: This output ramps from OV to 10V during a
sweep-up.
36. 10 MHz Oven Output: This signal is present only in
instruments with option 001. Normally it is connected
to the Ext Ref In connector (item 33) with a special
connector (HP Part No. 1250-1499) supplied with
option 001.
37. Marker: This TTL-compatible output goes low at the
selected marker frequency during a sweep up, and
high at completion of the sweep.
38. Power Transformer
1-3
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