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Pulse-position modulation (PPM) is a form of signal modulation in which M message bits are encoded by transmitting a single pulse in one of possible required time shifts. [ 1 ] [ 2 ] This is repeated every T seconds, such that the transmitted bit rate is M / T {\displaystyle M/T} bits per second.
The period of 20 ms (50 Hz) comes from the days where the signal was encoded in PPM (pulse-position modulation) format to be sent over the air. [10] The PPM period was around 22.5 ms, and the conversion to PWM was trivial: the time of the PWM high state was the time position of the PPM pulse for that servo.
At 10 000 ppm the solution is a deep red colour. As the concentration decreases the colour becomes orange, then a vibrant yellow, with the final 1 ppm sample a very pale yellow. In science and engineering , the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities , e.g. mole fraction or ...
Atomic clocks usually have an external PPS output, although internally they may operate at 9,192,631,770 Hz. [3] PPS signals have an accuracy ranging from 12 picoseconds to a few microseconds per second, or 2.0 nanoseconds to a few milliseconds per day based on the resolution and accuracy of the device generating the signal.
For example, switching only has to be done several times a minute in an electric stove; 100 or 120 Hz (double of the utility frequency) in a lamp dimmer; between a few kilohertz (kHz) and tens of kHz for a motor drive; and well into the tens or hundreds of kHz in audio amplifiers and computer power supplies. Choosing a switching frequency that ...
can be seen as a normalized measure of the energy per symbol to noise power spectral density (/): = where is the energy per symbol in joules and ρ is the nominal spectral efficiency in (bits/s)/Hz. [2]
UK broadcasters, alignment level is taken as 0 dBu (PPM 4 or −4 VU) The American SMPTE standard defines −20 dBFS as the alignment level. European and UK calibration for Post & Film [clarification needed] is −18 dBFS = 0 VU. US installations use +24 dBu for 0 dBFS. American and Australian Post: −20 dBFS = 0 VU = +4 dBu.
Electromagnetic (e.g. radio or light) waves are conceptually pure single frequency phenomena while pulses may be mathematically thought of as composed of a number of pure frequencies that sum and nullify in interactions that create a pulse train of the specific amplitudes, PRRs, base frequencies, phase characteristics, et cetera (See Fourier Analysis).