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FM Transmitter
Sistemas Electrónicos S.A EM 100 DIG
Technical Manual - v1.2 - November 2005
50
3.6 Control unit and display board.
This circuit board is basically simple.It contains the Microcontroller,the keyboard and few other circuits
which we will briefly discuss.Control & Display Units are shown in Figure 3-5 below. The Microcontroller
has 3 digital 8-bit ports and an analog one. This latter is the interface with the analog signals that
must be measured in the transmitter. A fast peak rectifier built around IC4 drives one of these analog
lines. All audio or baseband modulation plus some steady state signals are multiplexed to its input by
IC3, so requiring only one peak rectifier and increasing the number of the analog channels. One
analog channel reads the internal temperature through the optional TR3 sensor.
Figure 3-5: Detailed view of Control Unit.
The simple specialized IC6 performs clock and date functions as a stand-alone unit, backed-up by a
NiMnh battery which keeps circuit active for a long time when the power is removed.
Figure 3-6: Detailed view of Display & External Control board.
Elements numbered in Figure 3-6 are the following:
1
- MAIN/STANDBY push button switch.
2
- STANDBY indicator LED.
3
- ALARM indicator LED.
4
- VSWR indicator LED.
5
- LIMITER indicator LED.
6
- DISPLAY CONTRAST adjustment potentiometer.
7
- REMOTE operation indicator LED.
8
- LOCK indicator LED.