User's Manual

LBI-38636N
39
REMOTE CONTROLLER TO STATION
CONTROL PANEL ADJUSTMENTS
Although audio levels should be considered on a
system basis, it is appropriate to set the levels of the
remote controller and the control station panel by
themselves with reference to the levels required by the
transmission path and then connect the controller(s) and
station to the path. The transmission path, if it is more
than just a simple twisted pair, is usually set up with a
"test tone". The "average voice" level is defined as being
a certain number of decibels below the test tone. The test
tone is normally the maximum level that can be sent
through the path without clipping or being regulated.
Although there is no definite agreement on the difference
between the test tone and average voice levels, 10 dB is
an appropriate level.
In order to align the RCN 1000 Remote Controller
and T/R Shelf properly, it will be necessary to have some
information on the transmission path. This will help to
determine the levels at each end required by the system.
Specifications needed include:
1. Loss at 1 kHz
2. Test tone or maximum level
3. Average voice level (if defined)
4. Loss at 2175 Hz (if tone remote)
The DSP Board performs tone detection in a tone
remote installation. The "Secur-it" tone Decoder on this
board has a dynamic range of approximately 9 dB. The
system must be set up such that the "Secur-it" tones from
all remotes in the system arrive at the T/R Shelf within
this 9 dB window.
LINE OUT LEVEL ADJUSTMENT
U36-1 is used to set the line out level. Analog switch
U14 selects which audio source is routed to the line.
Possible sources are LOCAL MIC, VOL/SQ, auxiliary
receiver audio, auxiliary receiver audio summed with
VOL/SQ (simultaneous monitor), DSP LINE/TX
AUDIO, MODEM LINE data, OPEN (used for battery
alarm), GROUND (used for no transmission, and LINE
IN audio (used for four wire loop around). A battery
alarm tone and/or VG ALERT tone may also be summed
in with whichever source is selected with the exception of
GROUND. Typically LOCAL MIC, VOL/SQ, DSP
LINE/TX AUDIO, OPEN, GROUND, or LINE IN
AUDIO will be selected.
The gains in the circuitry are set such that 100
mVrms in on MIC HI or 1 Vrms (3 kHz deviation) in on
VOL/SQ HI (REPEAT AUDIO) will produce the same
line output level. The gains for VG ALERT tone and
battery alarm are also designed to provide the proper
levels without adjustments. The LINE output level should
be adjusted with a 100 mVrms, 1 kHz signal in on MIC
HI or a 1 Vrms, 1 kHz signal in on VOL/SQ HI.
LINE IN LEVEL ADJUSTMENT
Typically, the TX AUDIO and LINE OUT levels
should be adjusted prior to adjusting the LINE IN level.
DSP TX AUDIO and DSP LINE/TX AUDIO are
typically line audio or VOL/SQ HI audio that has been
processed by the DSP Board.
A DSP Board is always present, this DSP processed
line in audio will normally be selected by analog switches
U14 (DSP LINE/TX AUDIO to line out) and U15 (DSP
TX AUDIO to transmit audio) on the System Module
when line in audio is selected. The level for DSP TX
AUDIO and DSP LINE/TX AUDIO must be adjusted on
the DSP Board.
DSP LEVEL ADJUSTMENTS
The LINE IN level into the DSP must be adjusted
using U15-0 (DSP line cancellation level) and U15-1
(DSP line input level) located on the DSP Board. If two-
wire audio is used then both electronic pots must be
adjusted. If four-wire audio is used then only U15-1 needs
to be adjusted.
For two wire installations the DSP line cancellation
level pot (U15-0) is used to remove what the T/R Shelf is
transmitting on the line. While the T/R Shelf is
transmitting received audio down the line, the line
cancellation pot should be adjusted to minimize the signal
level at TP1 on the DSP Board. This leaves only what is
received from the remote. This signal is then level
adjusted using the DSP line input level adjust pot (U15-1)
and input into the DSP.
NOTE
System modules 19D902590G2, G3, &
G4 must have their cover removed to gain
access to TP1 on the DSP board. Modules
G6 & G7 have TP1 extended to the board
edge connector and may be metered on
the MASTR III backplane at J5, Pin 28A.
If four wire audio is used, the DSP line cancellation
pot must be set to zero.
The DSP also performs a compressor function on its
line input. The threshold for this compressor must be
adjusted as well. The line level should be adjusted on the
DSP Board prior to setting the compressor threshold.