The guy considered about E1 speed (Why),
One E1 has the speed of 2MBPS. The “why” is as under:
1. Human voice has frequencies upto 20KHz. Most of the “Information” is contained in frequencies 300Hz to 3700 Hz. So it is worth shedding up the rest of frequencies for effective use. This is done using band-pass filters.
2. Sampling is done, and according to sampling theorem, sampling frequency should be min 7.4KHz (ie, 2*3.7KHz). Standardization has been at 8KHz, ie one sample per 125us.
3. Then Quantization and Coding is done, converting one sample into a 8bit code. Therefore, one 8 bit code every 125us, or 64KBPS for one voice channel.
4.One E1 has 32 time slots with 8 bits each. Hence bit rate for an E1=
32 TS X 125us X 8bits= 2,048,000 bits/s
=2 MBPS