Rongge

Generated millions of times every day by our telephone keypads, the eight DTMF frequencies were chosen so that the harmonics and intermodulation do not generate significant in-band signal levels. The signal is encoded as a pair of sine waves, ensuring that no frequency is a multiple of the other and the sum and difference between two frequencies does not match any single tone and that’s why DTMF sounds so ugly!T he DTMF encoder circuit show n here is based on the HT9200B tone generator device produced by Holtek and distributed by Futurlec  among others. The encoder is complemented by a decoder elsew her e in this publication. 8-Channel DTMF : Encoder Schematic The HT2900B is supplied as a nice old fashioned 14-pin device. It can be instructed by a microcontroller to generate 16 dual tones and (in serial mode only) 8 single tones from the DTMF pin output . It s 8 - pin ‘ younger brother’ the HT9200A provides a serial mode only whereas the HT9200B contains a select-able serial/parall...

This project flashes eight LEDs in an apparently random manner. It uses a 4060 combined counter and display driver IC which is designed for driving 7-segment LED displays.  Circuit diagram : Simple 8 Random Flashing LEDs The sequence is not really random because seven of the LEDs would normally be the display segments, the eighth LED is driven by an output that is normally used for driving further counters. The table below shows the sequence for the LEDs. You can use less than eight LEDs if you wish and the table may help you decide which ones to use for your purpose.

This amplifier circuit has a power output of a small or too low at 5.8 Watt, which uses IC KA2205. The required voltage for at least 6 volts to 18 volts DC maximum. Schematics power audio amplifier with IC KA2205 Component List C1 = 1uF C2 = 100uF C3 = 47uF C4 = 1000uF C5 = 0.1uF C6 = 220uF IC1 = KA2205

This is an amplifier circuit based on IC AN374 which has a 1 Watt output power with supply voltage and a maximum of at least 8 volts to 16 volts with the DC current. Following amplifier circuit 1 Watt l 8 - 16 Volts Audio Amplifier. 1 Watt l 8 - 16 Volts Audio Amplifier