what is MFSK modulation
MFSK (multiple frequency shift keying), also called multi-frequency shift keying, is a method of signal modulation in which discrete audio tone bursts of various frequencies convey digital data. It was originally used by European and British government agencies in the mid 1900s. At that time it was called Piccolo, the name of the musical instrument whose high-pitched tones sound similar to an MFSK signal coming through the speaker of a radio receiver. MFSK is similar to frequency shift keying (FSK), but more than two frequencies are used. The most common form of MFSK uses tones of 16 frequencies and is called MFSK16. The tones are transmitted one at a time. Each tone lasts for a fraction of a second. The ratio of baud (the number of transitions per second) to bits per second (bps) is lower in MFSK than in binary digital modes. This reduces the error-producing effects of noise and interference for any given data speed. To provide still greater accuracy, forward error correction (FEC) is used
what is Digital certificate
In certain types of code scrambling, or encryption, a digital certificate validates that a public “key” to the code is owned by the entity sending the scrambled data. Digital certificates are issued by a certificate authority. They contain the public key as well as verification that the certificate is authentic and comes from the sender.