HP TM 11-6625-2779-14&P - Manual (Page 13)

Section III Model 3555B
SECTION III
OPERATING INSTRUCTIONS
3-1. INTRODUCTION.
3-2. The Model 3555B Transmission and Noise
Measuring Set is an extremely versatile transmission and
noise measuring set which satisfies many of the
requirements in testing telecommunications equipment.
The 3555B features a choice of 900 or 600 ohms bridging
or terminated for voice frequencies and 600, 135 or 75
ohms bridging or terminate for carrier frequencies. Noise-
to-ground and noise Metallic may be measured with 3kHz
Flat, C-Message or 1 5kHz Flat weighting. A HOLD
function permits seizing the line while measurements are
being made at voice and program frequencies. The set is
portable and operates from the internal battery, office
battery or ac power source.
3-3. This section of the manual contains all the
information necessary in the operation of the 3555B along
with a description of all controls, connectors and
indicators.
3-4. CONTROLS, CONNECTORS AND
INDICATORS.
3-5. Figure 3-1, 3-2 and Table 3-1 illustrate and
describe the function of all front and side panel controls,
indicators and connectors.
3-6. OPERATION.
3-7. To operate the Model 3555B, refer to figure 3-1
and perform the following steps:
a. Before connecting the 3555B to an ac power
source, insure that the 115/230 volt switch is
positioned to indicate the line voltage to be
used. Some earlier instruments did not have
the 115/230 volt selector switch. To change
these instruments, jumper wires must be
changed on the power transformer. Refer to
Appendix C for a wiring diagram of the two
configurations.
b. If the set is to be operated from the internal
battery or from an external office battery,
place the AC/BAT switch (located on the side
of the set) to the BAT position, using a small
pointed object; if the set is to be operated
from the ac line, place the AC/BAT switch to
the AC position. For operation from a 24 or
48V office battery, connect a patch cord with
a Western Electric 310 plug to the battery
jack on the side of the case and then connect
the cord to the office battery on the test
board or bay. Inserting the plug disconnects
the internal battery. The office battery is
arranged for -48V or -24V
±
2V with the
negative terminal of the battery connected to
the tip and the ground terminal connected to
the sleeve. Current consumption by the
3555B is approximately 15mA.
WARNING
DURING BATTERY OPERATION, THE
"G" BINDING POST MUST BE
CONNECTED TO EARTH GROUND.
CAUTION
THE CORD MUST BE CONNECTED TO
THE MEASURING SET BATTERY
JACK FIRST AND THEN PLUGGED
INTO THE BATTERY SUPPLY TO
AVOID SHORTING THE OFFICE
BATTERY TO GROUND.
c. Turn the POWER switch to ON and depress
the DIAL/BAT pushbutton on the FUNCTION
switch. The meter pointer should indicate in
the BAT GOOD area indicating that the
battery condition is good if the set is being
operated from the internal battery. The
meter will also monitor the ac supply voltage
or the external office battery voltage,
providing an indication of low voltage should
it exist. The voltage should cause meter
deflection above the lower end of the green
BAT GOOD area for proper set operation.
3-8. BATTERY.
3-9. The internal dry cell battery has a voltage range
between 45 volts when new to 24 volts at cut-off which is
the end of useful life. The cut-off voltage corresponds to
the left end of the green BAT GOOD area on the meter.
The condition of the battery and the approximate time to
cut-off can be estimated by observing the position of the
meter pointer in the BAT GOOD area.
3-10. The internal battery is of the carbon-zinc type with
its attendant limitations due to temperature. The service
obtained from carbon-zinc batteries depends on factors
such as current drain, discharge temperature, discharge
time and storage prior to use. The battery supplied with
the 3555B should provide in excess of 180 hours of
operation based on a 4 hours/day duty cycle at 77° F (25°
C). At other temperatures this time will change. At
temperatures above 131° F (55° C) the batteries may fail
suddenly while at temperatures below 40° F (-20° C), the
service life will be short.
3-1