NHRC-10 User Guide
Copyright
1999, 2000, 2001, NHRC LLC. All Rights Reserved.
Page 13
The transmitter mix bus is provided to the main transmitter through buffer amplifier U4A,
with it’s level adjusted with potentiometer VR5. The transmitter mix bus is also provided
to the remote base transmitter through buffer amplifier U4D, with it’s level adjusted with
potentiometer VR3. The transmitter mix bus is available for monitoring at connector J10.
Care must be taken to use a high-impedance load on J10 so the mix bus is not excessively
loaded.
The phone mix bus is sent to the phone line through buffer amplifier U4B.
Control receiver audio enters the controller through jack J8. If nothing is connected to J8,
then the remote base receiver audio is used for control receiver audio. Potentiometer VR4
sets the control receiver audio level into DTMF decoder U7.
Note
: the DTMF, courtesy tone and speech levels into the phone line are fixed levels and
are not adjustable.
The J10 header is a test point for monitoring the audio levels on the transmitter mix bus.
The audio at this point is biased at approximately 6 VDC and should be AC-coupled
through a capacitor if it is to be used with an amplified speaker for monitoring levels. Care
should be taken not to load the transmitter mix bus with a low-impedance load on J10.
Description of Controls:
VR1 sets the remote base receiver audio input level to the remote base receiver audio
processing circuit.
VR2 sets the incoming telephone level to the transmitter audio mix bus. Use this control to
increase or decrease the audio level coming in from the phone line.
VR3 is the remote base transmitter master audio level adjustment Use this to adjust the
remote base transmitter deviation.
VR4 sets the control receiver DTMF decoder input level. This control sets the audio level
into the Control receiver DTMF decoder U7. Set this potentiometer for reliable
DTMF decode as indicated by LED D12 lighting each time a DTMF signal is
received on the control channel.
VR5 sets the main receiver’s input level into the audio processing stage of the controller.
This pot is used as an attenuator to reduce (if necessary) the amplitude of the
incoming audio signal from your repeater receiver. This control will affect the main
DTMF decoder (U12) and will also affect the level of the receiver into the phone line.
Adjust this pot for good receiver drive down the phone line. Use VR7 to reduce
receiver level into the transmitter mix bus if necessary. (Note: see VR9 for more
phone line drive information.)
VR6 is used to adjust the level of the courtesy tone and DTMF tones into the transmitter
audio mix bus. Use this control to increase or decrease the level of the courtesy tone
and DTMF tones into the transmitter audio mix bus. This adjustment has no effect on
the levels of the courtesy tone or DTMF tones into the phone line.
