M805-00
ASP Card Operation
4.7
Copyright TEL
30/09/96
4.3
T805-01 Audio Inversion And
Recovery Modules (AIM & ARM)
In a typical Quasi-Synchronous system some, if not all, transmitters and monitor receiv-
ers will be remotely located from the site containing the TSGMs, LEMs and System Con-
troller. A microwave link or (more typically) land lines may be used to connect the
transmitters and monitor receivers with their LEMs. When land lines are used an AIM/
ARM combination is required between the LEM and transmitter or the monitor receiver
and LEM. The AIM/ARM pair is used because land lines have a satisfactory frequency
response only in the 300Hz to 3kHz band; any CTCSS or signalling in the 67-300Hz
band will be attenuated and distorted.
Audio, CTCSS and any signalling is passed from the LEM into an AIM where it is proc-
essed to adapt the signal for a 300Hz to 3kHz frequency bandwidth and so minimises
any possible effects that the link may introduce. It is then passed into the line connect-
ing to the appropriate site.
At this site the signal is passed into an ARM where it is recovered to restore the original
signal. If required, the signals are then separated (audio and CTCSS) and fed into the
transmitter. Control of the transmitter's key line is via the open collector "DIGOUT" out-
put from its ARM.
4.3.1
T805-01 Audio Inversion Module (AIM)
Figure 4.3 AIM Block Diagram
The AIM is operated in either the local or remote mode, although in most applications it
will be used in the local mode (i.e. it is at the same location as the TSGM(s), LEMs and
system controller).
1
A/D
Audio
amps
Audio
buffer
Audio
buffer
Audio
amps
A/D
Audio
buffer
Audio
buffer
Audio
amps
DSP
processor
D/A
D/A
Audio
amp
Audio
amp
Electronic
relay
Electronic
relay
1
3
4
2
1
2
N/C
ICCS
Combined HF and
LF audio
N/C
N/C
N/C
(Inverted)
HF/LF audio
Tx key
Summary of Contents for T805
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Page 44: ...7 18 Initial Programming Adjustment M805 00 30 09 96 Copyright TEL ...
Page 70: ...14 1 2 PCB Information M805 00 30 04 95 Copyright TEL ...
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