JK Audio RemoteMix Sport - Manual (Page 5)

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The receive side of RemoteMix Sport has a hidden fine tuning
control which is adjusted by inserting a small flat blade screwdriver
into the back of the unit just below the words Null Adj. and turning
left or right. This is a ten-turn potentiometer. This adjustment
controls the level of transmit audio that appears on the receive
audio jacks. The null circuit matches the characteristics of
RemoteMix Sport with the characteristics of the telephone line.
Although much of the transmit audio can be removed, this is not
the equivalent of a mix-minus output.
The amount of transmit/receive isolation will depend on the quality
of the telephone line. This circuit is factory set to give a good mix
on an average telephone line, and is therefore perfect for recording
both sides of a telephone interview.
To find the absolute null for any telephone line, follow this
procedure:
1. Place a call to a quiet location.
2. Send a signal down the line at moderate levels, this can be a
pre-recorded tape of music or speech, or preferably a test
signal.
3. Connect the Receive line output to a meter or scope, or listen
to the receive signal over the headphones. Be sure to turn up
the From Phone or Headphones volume control depending on
which method you are using to monitor the receive signal.
4. On the back of RemoteMix Sport, below the words Null Adj.,
there is a hole for a small flat blade screwdriver. This is a 10-
turn potentiometer to allow for very sensitive adjustments. Try
to remember the position of the blade, and the number of turns
you are making as you first adjust clockwise, and then back to
the original position, and then counterclockwise. The goal is to
adjust the null pot until the receive signal contains a minimum
amount of transmit audio. However, if you want a good mix of
transmit and receive signals, you must have someone on the
far end speak or send audio down the line as you adjust for the
proper balance.
To Reset Null to Factory Setting:
Disconnect from phone line, switch the Phone Line switch to On
Hook, and the set the null to minimum. This presets the null to an
average phone line impedance.
Hybrid Null Adjustment (optional)
5
Operation (continued)
Handset Interface
If you do not have access to an analog phone line or if the phone
system is a digital or analog PBX, ISDN, or a key telephone
system, you can use the built-in handset interface. Disconnect the
telephone handset from the coily cord and plug the cord into the
RemoteMix Sport PBX Handset Interface Jack. Now select the
handset type on the 3 position switch.
Trial and error works faster than a chart of handset types, but this
basic description may help.
Switch Position Handset Microphone Type
A Electret
B Dynamic
C Carbon
Talkback Feature
A built in speaker lets you monitor the phone line during call setup
and station breaks. The monitor speaker volume is controlled by
the headphone volume control and has an additional on / off switch
(near the A-B-C switch). An internal push-to-talk microphone (see
page 9) also helps when setting up your call. The speaker
switches off when the microphone button is pushed on to prevent
feedback.