What is modulation?
Pulse-code modulation (PCM) is a method used
to digitally represent sampled analog signals.
In a PCM stream, the amplitude of the analog
signal is sampled regularly at uniform intervals, and each sample is quantized
to the nearest value within a range of digital steps.
PCM streams have two basic properties that determine their fidelity to the original analog signal: the sampling rate, the number of times per second that samples are taken; and the bit depth, which determines the number of possible digital values that each sample can take.
PCM streams have two basic properties that determine their fidelity to the original analog signal: the sampling rate, the number of times per second that samples are taken; and the bit depth, which determines the number of possible digital values that each sample can take.
PCM – Pulse code
modulation has different available form which are used in real world, Let’s
learn about them;
What is PCM30C?
In PCM30C; the transmission is done in “32 time slots”. The timeslots are divided in 0-15 and 16-31 range of time slots respectively. As from the division of time slots, the time slots shows that the 0th and 16th time slots are for special purpose but rest of the time slots as 1-15 and 17-31 respectively.
- 30 time slots are reserved for data. In PCM30C; the transmission is done in “32 time slots”. The timeslots are divided in 0-15 and 16-31 range of time slots respectively. As from the division of time slots, the time slots shows that the 0th and 16th time slots are for special purpose but rest of the time slots as 1-15 and 17-31 respectively.
- The 0th and 16th time slots are for that purpose, which is given below: 0th bit is for Framing & control, sync byte and the 16th bit is for Signaling.
What is PCM30?
In PCM30, the transmission is done in the 32 time slots. The time slots are divided into 30(15-15) time slots.
As from the division of time slots, the time slots shows that the 0th and 16th time slots are for special purpose. but the rest of the time slots (30 time slots) are as 1-15 and 16-31 respectively, but the difference between PCM30C and PCM30 is the 16th time slot is divided into 2 parts as 4-4 bits.
- 1st 4 bits are used for signaling and rest 4 bits are for CRC.
- Rest of the features are same as PCM30C
In PCM30, the transmission is done in the 32 time slots. The time slots are divided into 30(15-15) time slots.
As from the division of time slots, the time slots shows that the 0th and 16th time slots are for special purpose. but the rest of the time slots (30 time slots) are as 1-15 and 16-31 respectively, but the difference between PCM30C and PCM30 is the 16th time slot is divided into 2 parts as 4-4 bits.
- 1st 4 bits are used for signaling and rest 4 bits are for CRC.
- Rest of the features are same as PCM30C
What is PCM31:
PCM31 is similar to PCM30 but the difference between PCM30 and PCM31 is due to the Signaling. This Signaling is present in the PCM30 and absent in the PCM31 mode.
NOTE: PCM31 and PCM31C is similar like PCM30 and PCM30C respectively
PCM31 is similar to PCM30 but the difference between PCM30 and PCM31 is due to the Signaling. This Signaling is present in the PCM30 and absent in the PCM31 mode.
NOTE: PCM31 and PCM31C is similar like PCM30 and PCM30C respectively
Unframed Modulation:
Unframed mode is totally different from PCM30/30C and PCM31/31C. In Unframed mode, all the 32 time slots are used for Data Transfer, there is no extra Burden of Framing & Control and apart from Neither there is Signaling concept nor the CRC concept is present.
Unframed mode is totally different from PCM30/30C and PCM31/31C. In Unframed mode, all the 32 time slots are used for Data Transfer, there is no extra Burden of Framing & Control and apart from Neither there is Signaling concept nor the CRC concept is present.
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