To send logical zero and logical one, at a long distance, this method is adopted. “Zero” is detected by sensing low frequency and “one” by high frequency. Frequency is transmitted on a long line without any change in its value and at the other end it is detected unambiguously.
Frequency shift keying is abbreviated as FSK. It uses frequency modulation technique.
- A PLL (Phase Locked Loop) IC, CD4046 is used to implement the circuit.
- Only the VCO (Voltage Controlled Oscillator) section of this IC is used to implement the circuit.
- The component values shown in the above diagram, produce two frequencies.
- 250Hz are generated when the key is pressed and pin no. 9 is connected to the circuit ground.
- 1.6KHz when pin no. 9 is connected to 9V, by not pressing the key.
- When the key is pressed the speaker produces bass sound.
- When key is not pressed, the speaker produces treble sound (i.e. sharp note).
- Depending upon the capacitor value tolerance, the frequency will change a little.
|2||IC socket||16 pin||1|
|7||PCB||general purpose, 4″X4″||1|
|8||Battery||9V, flat, with snapper||1|
|10||Speaker||8 Ohm,3 ” dia||1|
|11||Key (Button)||small, push to ON||1|
|12||Misc||solder metal, hook up wire|
This project is available in the kit form. Contact Omkar to buy it. This site has no commercial connection with his activities.