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Dual-tone multi-frequency signaling (DTMF) is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switching centers. [1]
Multifrequency signaling is a technological precursor of dual-tone multi-frequency signaling (DTMF, Touch-Tone), which uses the same fundamental principle, but was used primarily for signaling address information and control signals from a user's telephone to the wire-center's Class-5 switch. DTMF uses a total of eight frequencies.
Pages for logged out editors learn more. Contributions; Talk; Dual-tone multi-frequency
Tone remotes send commands to a base station using function tones, a series of two tones in sequence. The first tone is 2,175 Hz and is 100-300 milliseconds in length. [6] The most common second tone is 1,950 Hz. The most commonly used tone sequence in tone remote controls is the channel 1 transmit command.
Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies. MFSK is a form of M-ary orthogonal modulation , where each symbol consists of one element from an alphabet of orthogonal waveforms.
In dual-tone multi-frequency (DTMF) selective calling, the radio is alerted by a string of digits. Systems typically use 2- to 7-digits. Systems typically use 2- to 7-digits. These can be dialed from a traditional telephone dial connected to a radio or may be generated as a string of DTMF digits by an automatic encoder.
In MSK, the difference between the higher and lower frequency is identical to half the bit rate. Consequently, the waveforms that represent a 0 and a 1 bit differ by exactly half a carrier period. The maximum frequency deviation is δ = 0.25 f m, where f m is the maximum modulating frequency.
A low-frequency message signal (top) may be carried by an AM or FM radio wave. Waterfall plot of a 146.52 MHz radio carrier, with amplitude modulation by a 1,000 Hz sinusoid. Two strong sidebands at + and - 1 kHz from the carrier frequency are shown. A carrier, frequency modulated by a 1,000 Hz sinusoid.
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