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Wireless Intercom System
How to Set the Audio Control Switch Mode
One of the three modes previously mentioned may be selected (by jumpers) as follows:
1) Detach the QTR-2/QTR-600's battery cover and remove the two 9-volt batteries (if
installed). Remove the four small Phillips-head screws on the bottom of the unit and
carefully slide the internal chassis out of the case.
2) Locate the transmitter PCB's push-on jumpers (PCB with connections to the headset
connector and push-button switch). The jumpers are just behind the switch connector
(P2), near the battery terminals (refer to figure 1).
3) Set the CONT/PTT (P4) jumper as required (normally to the "CONT" position). In the
"CONT" position, the transmitter will always be "on" when the QTR-2/QTR-600 is
powered; in the "PTT" position, the transmitter will be "on" only when the button is
depressed.
4) Likewise, set the PT/PM jumper (P3) to the appropriate position. In the "PT" position,
the audio is enabled whenever the push button is depressed. In the "PM" position, the
audio is muted whenever the button is depressed.
NOTE: The push-to-mute ("PM") and push-to-talk ("PTT") modes cannot be used
together, because no audio would ever be transmitted.
An optional dual-mode switch is available for the QTR-2/QTR-600. This switch has a
miniature three-position rocker actuator and provides momentary operation on one side
and "locking" operation on the other side. The center position is "off," corresponding
to the "off" (not depressed) position on the push button. When this optional switch is
used, no "PTT" mode is available; that is, the transmitter will always be "on"
whenever the QTR-2/QTR-600 is powered.
5) While the transceiver is out of its case, adjust the microphone gain (R14), if
necessary (refer to figure 2). Accurate adjustment will usually require the use of a
deviation meter or service monitor. However, minor adjustments can be made by
comparing audio levels from two different portables via the master station monitor
circuits. Always make sure that gain is set while using the actual headset that will be
employed with the QTR-2/QTR-600.
NOTE: The QTR-2/QTR-600 portable has an audio compressor similar to those
normally used in wired-intercom remotes. Accordingly, it is easy to set the gain too
high, resulting in an increase in background noise when the user is silent, and in
"pumping" of the compressor during speech. Do not set the mic gain higher than is
necessary to achieve adequate volume at the master station.
6) If a deviation meter is used (the recommended procedure), adjust the mic gain control
for 3.5 to 4 kHz deviation at normal user speech levels.
7) Do not adjust any controls on the QTR-2/QTR-600 receiver, as there are no user-
adjustable controls on this PCB. Misadjustment will likely require an expensive and
time-consuming return to an authorized service location or to the factory.
8) Return the QTR-2/QTR-600 to its case, making sure to feed the antenna wires or BNC
connector carefully through the holes in the bottom of the case.
The QTR-2/QTR-600 includes a small "power on" LED indicator near the volume control.
This LED has no function except to show the unit is powered. Unless the "PTT" mode has
been selected, this will also mean that the portable is transmitting.
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