P.4.1.3
TYPE 1/TYPE 2 FAULT Inputs
These inputs generate an “INHIBIT K2-L” signal at U52-8 and
cause the same circuit action as described for “Transmitter
Turn-Off.” If K2 has not yet energized, a “CLEAR-L” signal
at U53-11 clears the Turn-On one-shot which stops the turn-on
pulse and de-energizes K1. Further action is as follows:
a. TYPE 1 FAULT: A TYPE 1 FAULT generates a latched
OFF command.
b. TYPE 2 FAULT: A TYPE 2 FAULT generates an OFF
command, then recycles the transmitter ON after approxi-
mately 2.4 seconds. If the fault is repeated, the TYPE 2
FAULT becomes a TYPE 1 FAULT and generates a
latched OFF command. TYPE 2 FAULTS includes rf
overdrive, rf underdrive, and supply current overloads.
P.4.2
Transmitter Power Control Logic
Normal logic flow will be described for a local or remote control
LOW, MEDIUM or HIGH input. The RAISE/LOWER control
inputs are active only if the transmitter is already ON in the
LOW, MEDIUM, or HIGH power level mode.
Refer to Figure P-2, Power Control Logic, Simplified Diagram;
Figure P-3, Power Control Section Block Diagram; and Figure
P-4, Controller, Command Input Circuit.
a. CONTROL INPUT Occurs. A LOW, MEDIUM or HIGH
control logic HIGH input is generated from a front panel
button or from a remote control input.
b. INPUT CIRCUITS: The logic HIGH input turns on a
transistor switch input circuit which generate a logic
LOW output to Switch Debounce U45.
c. SWITCH DEBOUNCE: Possible “contact bounce” from
the input is eliminated.
d. PRIORITY ENCODE/DECODE SELECT: Approxi-
mately 20 milliseconds after a control input occurs, a
single “priority selected” command appears at decoder
U42 output. A decoder output is present only while a
control input is present. The RAISE/LOWER decoder
output commands are active only if the transmitter is
already ON. The decoder output OFF, HIGH, MEDIUM,
LOW commands are applied:
1. To Power Level Change Gate U57, pins 9, 10, 12, and
13.
2. To Power Level Latch U40.
e. POWER LEVEL CHANGE PULSE. A HIGH, ME-
DIUM, or LOW command is applied to the delay and
pulse generator circuit and the inhibit power level change
gate U57. This generates a Power Level Change pulse
about 20-30 milliseconds after it appears at the Decoder
output. When a pulse occurs, it goes to circuits which:
1. Clock the Power Level Latch U40.
2. Generate a Data Strobe pulse (U13-8 and U62-10).
f. POWER LEVEL LATCH: The HIGH, MEDIUM, or
LOW command appears as a logic HIGH output from
U40 when the latch is clocked by the Power Level Change
pulse.
g. INHIBIT GATES: The inhibit gates prevent the LOW,
MEDIUM or HIGH command from generating a “TURN
ON REQUEST” signal if there is FAULT present. The
command then goes to:
1. Turn-On Request Gate, to generate a “TURN-ON
REQUEST” to the turn-on/turn-off control logic.
2. Status Indicator Circuits, to illuminate the front panel
button and provide remote status output.
3. Counter Input Gates, to route clock pulses to the
correct counter when a RAISE or LOWER command
is given.
4. Multiplex Address Inputs, to select correct BCD out-
put for power level chosen.
h. Turn On Request Gate (U52-12): The latched LOW,
MEDIUM or HIGH command to the inputs of U52 will
cause the output to go LOW. This LOW signal is inverted
by U55-12 and becomes the “TURN-ON REQUEST-H”
signal to the Turn-On/Turn-Off logic.
i. Multiplex (U21-U23, U13-U15 and U33-U35): The
latched LOW, MEDIUM or HIGH command immedi-
ately selects the multiplexed address of up/down counter
U6, U7, or U8. The counter contains a user programmed
12-bit BCD number to set the LOW, MEDIUM or HIGH
power level on the Analog Input Board.
j. Up/down counter input gates (U2, U14 and U26): The
latched LOW, MEDIUM or HIGH command enables the
corresponding counter input gates. These gates route a
clock pulse to the UP or DOWN inputs of the HIGH,
MEDIUM or LOW BCD counters when a RAISE or
LOWER command is generated.
k. Up-down counters: There are three up-down counters,
one each for HIGH, MEDIUM and LOW power levels.
Outputs and inputs are:
1. OUTPUTS: Each up-down counter always has a 12-
bit BCD output (the last power output data set in that
counter), unless the backup supply fails. If the trans-
mitter is in the HIGH, MEDIUM, or LOW power level
mode, that counter’s output is selected by the Multi-
plex and goes to input latches on the Analog Input
Board.
2. INPUTS: Each counter can count UP or DOWN when
clock pulses are sent to its count-up or count-down
input, and transmitter power changes as the counter
“counts."
The clock pulse will change the BCD number stored in the
counter, thereby changing the power level of the LOW, ME-
DIUM or HIGH position. If the transmitter is OFF or if a RAISE
or LOWER command is not present, there is no clock pulse to
any counter.
P.4.2.1
Power Level Change, with the Transmitter ON:
When power level is changed by pressing the HIGH, MEDIUM,
or LOW button while the transmitter is ON, the switch will
illuminate and the transmitter power output will change. In the
turn-on/turn-off circuit, a new “TURN-ON REQUEST” is re-
DX-25U
P-4
888-2297-002
Rev. S: 05-02-97
WARNING: Disconnect primary power prior to servicing.
