Codan Radio MT-3 - Manual (Page 18)

USER GUIDE | MT-3 ANALOG RADIO SYSTEMS
Chapter 2: Technical Information Page 10
AM Front Panel Frequency Selection
The AM receiver and transmitter have a Frequency Select Handle that allows the user to select and
display the frequency of Channel 16 on the front panel of the module. The frequency selection is
achieved by pushing the up arrow or down arrow keys to increase or decrease the frequency. On
older motherboards (Serial # 123125 and earlier), jumper JU73 on the subrack / motherboard must be
installed for this operation. The frequencies of channels 1 through 15 are programmed the same as
all other MT-3 modules. Figure 2-1 shows front panels of the AM receiver and transmitter and a larger
representation of the Frequency Select Handle.
Figure 2-1: AM Front Panel Frequency Select Handle
CTCSS and DCS
CTCSS and DCS decoding and encoding is performed by a separate circuit board mounted in the
control card. The receiver and transmitter modules do not typically contain the CTCSS and DCS
decoder or encoder capability, although this can be installed if the system confi guration requires it (eg.
A voter system with no control card).
The CTCSS / DCS subtones are sent to the decoder from the receiver using the discriminator audio
signal line and the receiver is controlled by the decoder via a receiver mute line that overrides the
squelch circuitry. Subtones from the CTCSS and DCS modules are sent to the transmitter using the
subtone 1 input signal line. This style of connecting the CTCSS / DCS externally from the receiver and
transmitter allows for a greater fl exibility for custom confi gurations.
A receiver could be confi gured so that one of two different CTCSS tones would unmute it, or a repeater
could be confi gured such that a link transmitter could be activated only when a specifi c CTCSS or DCS
subtone is received.
T X
REFERENCE
INPUT
OFF
KEY TX
MIC
RF OUT
NORM
TRANSMITTER
1 2 8.0 0 0 0
*
SQ . DI SA B L E
N
O
RM O
F F
RF N I
REFERENCE
INPUT
RECEIVER
1 2 8.0 0 0 0
*
1 2 8.0 0 0 0
*
FREQUENCY (MHz)
MADE IN CANADA
MODEL # CODE
MADE IN CANADA
MODEL # CODE
FREQUENCY (MHz)