Pub. 42004-139D
GAI-Tronics 700 Series Page/Party
®
Systems
Page: 5 of 10
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Step 6 — Checkout and Adjustment
Test all field wiring connections (page line, party line(s), mute, ac power and speaker) between stations,
and complete the line balance assembly installation before checkout begins. Ensure that all handsets are
on-hook.
1.
Apply ac power, and check the station next to the line balance assembly.
2.
Press the “push-to-page” switch (in the handset handle on some stations) and speak directly into the
microphone of the handset. The broadcast should be heard at all paging speakers in the system except
those associated with the station under test. If working properly, very little or none of your own voice
(sidetone) is heard from the handset earpiece. If the line balance assembly is not connected properly,
there will be a high level of sidetone, perhaps enough to cause feedback. Adjust the line balance
assembly to optimize sidetone rejection on the page line. If the system is complete when the first
station is checked, adjust the line balance assembly as noted below.
Do not adjust station
(amplifier)
controls until the line balance assembly is adjusted.
3.
Release the push-to-page switch and check the party line(s) sidetone level by speaking into the
microphone of the handset. If working properly, very little or none of your own voice is heard from
the handset earpiece. This sidetone rejection will only occur if the line balance assembly is properly
connected because it contains a fixed resistor load for each party line. In addition, no party line
adjustments are provided. Check party line operation by conversing between two or more stations.
Adjustment of the Line Balance Assembly
To set the control for proper page circuit loading:
1.
Remove the line balance assembly cover to expose the line balance control.
2.
Lift the handset from the adjacent handset hook and press the push-to-page button.
3.
From the normal speaking distance (approximately ½-inch), blow steadily into the handset
microphone and adjust the control to minimize receiver sidetone. This adjustment needs to be made
only at the initial installation of the system. However, if in the future more than 10 speaker amplifiers
are added or deleted, repeat adjustment of page circuit loading.
4.
After final adjustment, replace and secure the cover with the four mounting screws to discourage
tampering by unauthorized personnel and prevent entry of contaminants.
Each amplifier has a paging speaker volume control. It is accessible from the front panel with a
screwdriver, but is concealed behind the metal nameplate. To reach it, simply loosen (do not remove) the
two nameplate screws and pivot the nameplate around the left screw. This control is adjusted at the
factory so that a moderate page level produces 4 watts of output power.
Each handset/speaker station amplifier has two additional internal controls: receiver volume control and
receiver sidetone control, both accessible using a screwdriver through the holes in the chassis. A third
hole allows similar access from the rear of the paging speaker volume control. Both controls are
factory-adjusted for optimum results in most industrial applications. Do not readjust these controls to
solve system problems until other possible faults are checked, such as a missing, defective, or improperly
connected line balance assembly. There is very little drop in receiver (handset earpiece) volume level due
to system cable losses. Generally, the only reason to reset the receiver volume control is to compensate
for extremely high ambient noise levels (up to 110 dB) or to meet particular personnel needs.
At stations with cable lengths of 3,000 feet (1 km) or more from the line balance assembly, receiver
sidetone rejection is noticeably affected by cable impedance. Use the receiver sidetone control to
compensate for this by rotating the control clockwise approximately 60 degrees for 3,000 feet (1 km) of
cable length.
