Operating instructions

OPERATING MANUAL 2945A
46882-311D 3-7
undefined signal, or assessing the squelch operating level of a receiver. It has no mechanical
stops. This control is also used to select items or digits from displayed lists, in conjunction with
TONES and SYSTEM modes.
(10) Audio connections.
AF GEN OUT socket. The signal available at this BNC socket is the combined output from both
or either of the AF generators and/or the tones generator.
AF INPUT socket. Signals fed into this BNC socket can be measured using the AF counter, the
AF voltmeter and the distortion measuring circuits. It is also the input for the digital
oscilloscope.
ACCESSORY socket. Used for connecting Directional Power Heads and other accessories. The
presence of these is automatically detected. The socket is also used for direct connection of a
headset, allowing modulation of the signal generator by a microphone and audio signal
monitoring through headphones.
When using the accessory microphone with PTT switch, automatic switching between Tx and Rx
modes using the PTT switch is possible.
DISPLAY HOLD key. To the left of the variable control is the [DISPLAY HOLD] key. Pressing this
key at any time will freeze the display and prevent any adjustment to parameters displayed on the
screen. The soft key menu changes to show two keys, [Store] and [Print].
The [Store] key, gives access to the
STORE/RECALL screen and menu. The use of this feature is
explained on page 3-82
The [Print] key is used to start the Screen Print function. This causes a hard copy of the held
screen to be printed onto a suitable printer. If the memory card option is fitted, the current time
and date, as held in the Real Time Clock, are printed on the hard copy.
The use of the Screen Print feature is explained under the heading ’Printer’ on page 3-89.
AC/DC. AF input coupling option key Located above the AF input socket, this key toggles the AF
input circuit between direct and capacitive coupling. The option selected is displayed on the
screen.
(11) Memory card slot. Instruments with the optional memory card interface fitted, can make use of
memory cards for the storage and retrieval of results and settings.
Details of the use of memory cards is given under later in this chapter under Stores, settings and
results on page 3-82 and Memory Card on page 3-84.
(12) Volume. This control varies the level of the AF signal fed to the loudspeaker.
(13) RF receiver squelch level control. When monitoring the demodulated output through the
loudspeaker or headphones, the RF level below which signals are isolated from the AF circuits
can be controlled. Clockwise rotation of the squelch control raises this level and anti-clockwise
rotation decreases it.
(14) Scope trace vertical position. This adjusts the vertical position of the trace within the graticule.
(15) Oscilloscope sweep mode keys. The [SINGLE] and [REP] keys, located above the scope vertical
position control, select the oscilloscope sweep mode.
(16) Test mode select keys. On the left of the front panel are six blue keys. These are the ‘Test Mode
Select’ keys, used to put the instrument into one of the basic test modes. They are active
whenever the instrument is powered up and under local control.
(17) HELP/SETUP key. Above the test mode select keys is the ‘HELP/SETUP’ key.
Pressing this key will cause the HELP/SETUP access screen to be displayed if the instrument is
under local control. This does not interrupt any on-going function of the Service Monitor. See
HELP/SETUP on page 3-10
When the instrument is under remote control, pressing this key will return control to LOCAL
unless an instruction to prevent local operation has been sent from the remote control device.