M
IDIAN
E
LECTRONICS
I
NCORPORATED
P
AGE
5
DDU-100/200
Manual
3.2 J
UMPER
S
ETTINGS
There are two user configurable jumpers, JU1 and
JU4. Both are installed at the factory. JU1 allows
signaling audio to be heard in the local speaker. If this
is not desired, cut JU1.
JU4 controls the output impedance of transmit audio.
See
OUTPUT LEVEL
below to determine if JU4 will
need to be cut.
3.3 A
DJUSTMENTS
Once the unit has been connected to the radio, several
adjustments must be made to achieve proper
operation. It will be necessary to open the unit. Use the
pictorial to identify the location of the following trim
pots: R2 and R32 near connector P3, R51 near IC U6,
and R105 near the volume control.
INPUT LEVEL (when using decode feature)
Use a service monitor to generate a 1000 Hz test tone
at 2/3 of maximum system modulation (typically 3.3
kHz). Measure the voltage appearing at TP1 and
adjust R2 such that TP1 is at 250mV RMS.
OUTPUT LEVEL (when using encode feature)
Use a service monitor to measure the modulation level
generated by the DDU. Cause the DDU to generate
tones by typing in a few digits and pressing <SEND>.
Adjust R51 so that the modulation level is at 2/3 of the
maximum system modulation (typically 3.3 kHz).
If the output level cannot be adjusted low enough, it will
be necessary to cut JU4. This changes the output from
low impedance to high impedance.
Tip:
EIA format tone 3 is 1023 Hz. Programming the
encode format to EIA and setting encode time to 2000
milliseconds provides a handy test tone. Simply enter
the digit 3 and press <SEND> for 2 seconds of test
tone.
SPEAKER PRE-AMP
Though the DDU has a volume control knob, it also
has an input audio pre-amplifier. While listening to
audio on the channel, adjust R32 so that the minimum
and maximum volume control settings are at desired
levels.
3.4 C
ONFIGURATION
S
ETTINGS
Once adjustments have been made, it will be
necessary to configure the DDU to meet the system
requirements. This is done via
Menu Mode
. The most
crucial settings include
Decode Format
and
Encode
Format
(if using encode feature). Refer to
ENC/DEC
SETUP
menu item. Pay close attention to
Encode
Time 1 & 2
and
Decode Time
as well.
It is also important to program
COR Polarity
to match
that of the radio. If this is not set properly, the DDU will
not decode some of the formats.
Be sure to set the time of day via
TIME SETUP
once
the DDU is operating as desired. Once the time is set,
be sure to leave the unit on at all times or else the time
will have to be reset. The time can only be set to the
nearest minute. Seconds are kept track of internally
and start running the instant the unit is turned-on. It is a
good idea to check the time clock monthly as crystal
and temperature variances affect the accuracy.
4 BASIC
OPERATION
4.1
D
ISPLAY
M
ODE
The DDU operates either in
Display Mode
or
Menu
Mode
. In display mode, the DDU normally displays the
last ANI received.
4.1.1 Reading the Display
ID (ANI) –
This is the numeric ID (or ANI) of the user
who last transmitted on the channel. When the
Status
Feature
is enabled, this area will alternate between
displaying the ANI and the status message every 2
seconds.
TIMESTAMP –
This is the time of day that the last ANI
was received. The timestamp is in 24-hour format. In
24-hour format, 4 A.M. is displayed as 04:00 and 4
P.M. is displayed as 16:00.
Note that the timestamp
changes only when a new ANI comes in, it is not a
time-of-day clock.
USER NAME –
This is the name of the user
associated with the numeric ID that was received. User
names are stored in a database. The database must
be configured before names can be displayed.
SCROLL LEFT INDICATOR –
Indicates that there are
other ANI’s previously logged. Press the left
<SCROLL> button to view the previously logged items.
