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433.92 MHz FM Data Transmitter
- 433.90 MHz (TTL High Input)
- 433.94 MHz (TTL Low Input)
The low and high pulses are encoded with frequency shift keying.
A possibly student-proof module.
- R2 limits the input current to a low level
- The transistor (BC182L) buffers the input and pulls the data input low when the TTL input is high.
- R3 is a pull up resistor.
- C1 is a decoupling capacitor.
- D1, D2 and D3 act like a Zener diode to prevent the potential on pin 4 (the power supply) rising above 3.4 Volts.
- R1 limits the power supply current to about 16mA. The RTFQ module takes about 8mA and the LED circuit takes the rest.
- D7 is a polarity protection diode.
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