LOW-FREQUENCY AMPLIFIER
31
5.1.2. GAIN SETTING
1.
Press "F2". The field "Gain" will become lighter.
2.
By means of the
buttons to set gain value in dB (0, 5, 10, 20, 30, 40, 50, 60)
which will be displayed on the indicator (Fig.37, item 7).
3.
Finish the adjustment ("F2"). The field "Gain" will become darker.
The set gain value remains unchanged until its next correction or power off.
5.1.3. BIAS VOLTAGE SETTING
1.
Press "F3". The field "Bias" will become lighter.
2.
By means of the
or
buttons set bias voltage value (from -26 V to +26 V with a step
of 2 V) which will be displayed on the indicator (Fig.37, item 8).
3.
If necessary to change the bias voltage polarity, press
or
buttons
4.
Press "ENTER" for set value of bias voltage equal "0".
5.
Finish adjustment ("F3"). The field "Bias" will become darker.
When setting gain or bias voltage, all buttons that are not involved in these
procedures are blocked.
When bias voltage is supplied to the cable, the gain will be automatically reduced to 25 dB (if a
higher value was previously set). If the connected pair voltage is more than ± 3 V (DC), the bias
voltage supply is automatically blocked.
The field of the "F3" button takes a form:
In this case, for supplying of bias voltage it is necessary to disconnect the cable from the
power source (to isolate a cable).
The set value of bias voltage remains unchanged until its next correction or power off
5.1.4. AUTOMATED MODE
For automated search in all possible combinations of wires of a multi-wire cable press "F4"
("Scan All"). The built-in Electronic Switch in turn the connects pairs of wires. The tabular cursor
is set to the row corresponding to the connected pair of wires. Scanning stops for a few seconds
to analyze the received signal by ear.
After the end of the scan cycle, the tabular cursor is set to an initial row (on which it was set
prior to scanning).
If during scanning on any pairs suspicious signals were detected, after the end of the cycle, it
is necessary to set the cursor on the corresponding line in the table and analyze this signals using
an OSCILLOSCOPE and a SPECTRUM ANALYZER.
5.1.5. OSCILLOSCOPE
For turn on an OSCILLOSCOPE it is necessary to press "F1" in the LFA main menu.
OSCILLOSCOPE screen is shown in Fig.38.
