TN811 SM-3 System Regulator
MT-3/4 Radio Systems
TECHNICAL NOTES
Page 1 of 2
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CODANCOMMS.COMTECHNICAL NOTE:
TN811, REV 3-1-0, © Mar 2013
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The SM-3 system regulator is a plug-in module which provides voltage regulation, system metering and audio
monitoring for an MT-3 or MT-4 radio system. The SM-3 includes the following features:
• High current +9.5 Vdc voltage regulator with an anti-latchup hysteresis circuit.
• Front panel switch selectable meter outputs to check supply voltages, carrier strengths, etc.
• Audio amplifi er and loudspeaker.
• Relay drivers for optional antenna relays.
There are four diff erent versions of the system regulator.
SM-3-H0-014-00 Standard SM-3 with no relays or switches (14 HP width)
SM-3-H0-014-01 SM-3 with main power switch (14 HP width)
SM-3-H0-R1N-00 SM-3 with single antenna relay on the front panel (21 HP width)
SM-3-H0-R2N-00 SM-3 with dual antenna relays on the front panel (21 HP width)
The System Regulators have a rotary switch on the front panel allowing the various functions to be selected
for monitoring. Two front panel jacks are provided for monitoring of selected functions. An audio amplifi er and
loudspeaker allow for audio monitoring. Front panel controls allow for audio volume adjustment. Select the Receiver
audio for monitoring using the rotary switch (position 3 for Receiver A, position 5 for Receiver B), and turn the
speaker ON. An external speaker jack is also available. An LED indicator illuminates when the audio circuits are
on. Receiver C, D and E can also be monitored when using the System Regulator in a Multiple Receiver Subrack.
Jumpers JU15 - JU24 are installed for Multiple Receiver Subrack compatibility.
Backwards Compatibility
The SM-3 System Regulator is a direct replacement for the SM-3 System Monitor, however, the rotary switch
positions for the front panel test points have been changed.
The simplex mode jumpers to connect the Transmitter PTT OUT signal line to the RX MUTE are now located
on the new motherboard, but the System Regulators still contain the simplex mode jumpers for backwards
compatibility with older motherboards.
2
1
5
4
3
67
8
11
10
9
FUNCTION
12
SYSTEM REGULATOR
MADE IN CANADA
VOL METER
+
-
ON
OFF
SPKR
INT
EXT
EXT
SPKR
ANTENNA A ANTENNA B
RX A RX B
TX A TX B
2
1
5
4
3
67
8
11
10
9
FUNCTION
12
OFF
VOL
SYSTEM REGULATOR
METER
+
-
MADE IN CANADA
ON
OFF
SPKR
INT
EXT
EXT
SPKR
POWER
ON
VOL
SYSTEM REGULATOR
METER
+
-
MADE IN CANADA
ON
OFF
SPKR
INT
EXT
EXT
SPKR
OFF
POWER
ON
2
1
5
4
3
67
8
11
10
9
FUNCTION
12
2
1
5
4
3
67
8
11
10
9
FUNCTION
12
SYSTEM REGULATOR
MADE IN CANADA
VOL METER
+
-
ON
OFF
SPKR
INT
EXT
EXT
SPKR
ANTENNA A
RX A
TX A
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