What is PCM?
PCM is Pulse Code Modulation. The volume of the sound is sampled at regular intervals, extremely frequently – thousands of times per second. Each sample is converted into a binary number and that is stored in the file or transmitted. In order to play back the data, each binary number is converted to an analog voltage, at the same rate as was used during recording. I believe that PCM is the simplest, uncompressed method of holding sound information, as used in conventional WAV files.
PCM stands for Pulse Code Modulation. PCM in R/C is actually no closer to an accurate description than PPM! PCM is another encoding scheme, not a modulation scheme. By 1981, before PCM was introduced, we modelers were permitted to use Frequency Modulation as well as AM. The FM R/C system actually uses FM/FSK where FSK stands for Frequency Shift Keying. FM/FSK is also used for PPM encoding. This simply means that, for each modulation pulse, the frequency of the transmitted signal is shifted about 3KHz; from 1.5 KHz above to 1.5 KHz below the center frequency. The other variant is that some manufacturers shift from low-to-high vs. high-to-low just to be different from the competition. True PCM in the normal communications lexicon means that an analog signal is sampled periodically and its amplitude is converted to a digital word of a certain length; i.e., the greater the amplitude, the higher the digital number. Several channels can be multiplexed and merged with a “start bit” and “end b
