ZETRON 37-MAX, Installation Manual, Page: 23 / 90

Section 3. Operation
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signal has stopped, the panel will function again normally the next time carrier with a valid
tone or code is received. As the timer nears its limit, the panel will start transmitting warning
tones to indicate that it is about to drop the transmitter.
This timer is not intended as a way to limit users from getting long winded. The Repeater
Time-out timer is intended to help protect the repeater transmitter equipment in case of a
"stuck mic" accident. This is particularly important for repeaters that use lower power radios
which are not designed or rated for continuous-duty operation.
DCS Polarity
If you look at Table 3. OPERATION -2, you will notice that each of the three-digit DCS
codes has an 'inverted' code next to it. The number in the inverted column is the valid DCS
code number that would be decoded if you took the original code in the first column and
inverted it, that is, changed all the zeros to ones and vice-versa.
The reason this is of interest to a technician working with the Model 37-MAX (or another
repeater controller) is because most analog amplifier stages are also signal inverters, and any
time that a signal carrying the DCS encoding passes through a stage all of the data bits in the
DCS code get flipped upside down, i.e. inverted. If there is an odd number of stages between
the encoder and the decoder, the decoder will see the inverted code and fail to provide a valid
decode output. This problem can arise going in either direction, the panel can fail to decode
the DCS sent by the radio user, or the radios in the fleet can fail to decode the signal from the
repeater.
One way to handle this problem, once the technician has determined which is failing, the
encode or the decode, is to look through Table 3. OPERATION -2 and enable the user
number that has the necessary code in its Inverted column, or use the tone translation
command to set the enabled user's encode to the necessary inversion. This is not a good
solution if the system is supporting very many DCS users.
The Model 37-MAX offers a simple fix for this problem. Since the decode/encode inversion
is the result of the physical design of the radio hardware and the tone panel's interface to
them, if any of the DCS codes are inverted, then they will all be inverted. The 37-MAX has
two complementary sets of commands in its system programming that will independently
configure the DCS decoding and encoding done by the panel to be either 'normal' or
'inverted'.
Repeater Knock-down and Setup
There are any number of reasonable scenarios where a system operator might want to
temporarily take a repeater out of service, that is, force it to be idle. One way to do this would
be to enter the programming mode and force all programming back to the factory default
values. This method carries the high price of requiring the technician to completely
reprogram the 37-MAX in order to return it to service.