Key features

• •Dual tone signal decoding and encoding;Remote control device;Signal generator
• •The keystroke or digital information is converted into a two-tone signal during encoding and transmitted, and the existence of the keystroke or digital information is detected in the received DTMF signal during decoding.
• •A DTMF signal is made up of audio signals of two frequencies. The frequencies of these two audio signals come from two pre-allocated frequency groups: a row frequency group or a column frequency group. Each pair of such audio signals uniquely represents a number or symbol.
• •There are usually 16 keys in the telephone, including 10 numeric keys 0-9 and 6 function keys *, #, A, B, C, D. According to the combination principle, there should be 8 different single audio signals. Therefore, there are also 8 kinds of frequencies that can be used, so it is called multi-frequency, and because it uses any one of the high and low frequencies to arbitrarily select the combination for encoding, it is also called "8 out of 2" encoding technology.
• •According to CCITT's recommendations, the internationally adopted multiple frequencies are 697Hz, 770Hz, 852Hz, 941Hz, 1209Hz, 1336Hz, 1477Hz and 1633Hz. With these 8 frequencies, 16 different combinations can be formed, which represent 16 different numbers or function keys.