12) Adjust, if necessary, the intercom input and output levels via the I/C IN and I/C OUT
controls. In general, the output control should be set so that wireless users have the
same apparent volume in the wired system as wired users. In the same manner, the
input level should be set so wired users have the same apparent volume in the wireless
system as the wireless portables.
13) If necessary, the “MON” function can be selected (“LOC/MON SEL” switch “out”) to
allow individually monitoring the I/C, link, and wireless portables to locate a problem.
This mode should also be used to “close” the mic in the headset during use of the
system, to prevent pickup of extraneous noise.
14) The wireless-intercom system should now be fully operational.
Headset Compatibility
As normally shipped, the QTR-2/QTR-600 and the QX-6A/QX-600 are configured for
compatibility with standard Clear-Com headsets with 4-pin full-sized XLR connectors.
These headsets have 50- or 200-ohm receivers and low-impedance dynamic microphones.
Headsets with higher impedance receivers can be used, but lower headset volume will
result. Use of headsets with impedances below 50 ohms is not recommended for the
QTR-2/QTR-600 because of reduced battery life, but impedances as low as 8 ohms are
acceptable for the QX-6A/QX-600.
The QTR-2/QTR-600 and QX-6A/QX-600 are also compatible with headsets equipped with
most types of electret mics. Units with two- or three-wire interfaces (e.g., with bias voltage
supplied on the signal lead or with a separate bias connection) are accommodated. In this
configuration, the receiver audio is single ended and will be considerably lower in level than
for the balanced configuration described above. Only headsets with high-efficiency receivers
should be used if high-earpiece volume levels will be needed.
There are several provisions in the QTR-2/QTR-600 and the QX-6A/QX-600 to
accommodate either dynamic or electret microphones. Connections from the headset to the
XLR connectors should be as shown in the following chart:
Pin No.
Function
Dynamic Mic
Electret Mic*
1
Mic ground
Bias
2
Mic audio
Mic Audio
3
Headset receiver (hi)
Headset receiver
4
Headset receiver (lo)
Common ground
*In the case of a two-wire electret, a 1000-ohm resistor must be installed in the XLR
connector between pins 1 and 2.
Table 2
The receiver output in the dynamic-microphone mode is balanced; that is, neither side is
grounded. Therefore, pins 3 and 4 may not be common with pin 1 (mic ground) or with the
connector shell. If this is done, low and distorted audio will result.
Other changes are necessary to convert the QTR-2/QTR-600 or QX-6A/QX-600 to operate
correctly with headsets or electret mics. In the QTR-2/QTR-600, the HEADSET
INTERFACE CONNECTOR, P1, must be installed in the correct position for dynamic or
electret mics. In addition, the GAIN SELECTOR for the mic preamp must be changed; this is
accomplished by moving the P6 jumper plug on the QTR-2/QTR-600 transmitter PCB. Refer
to Figure 2 for correct connector and jumper-plug installation.
In the QX-6A/QX-600, switch block S15 is provided to configure the local headset
connector to accommodate headsets with either dynamic or electret mics. Refer to Table 3
for the proper switch settings, and to Figure 3 for the location of S15.
Wireless Intercom System
9
