Transmission Circuits DS-1, DS-3, T-1, E-1

DS or Digital Signal, are categorized into 7 categories. the DS0, DS1, DS1C, DS2, DS3, DS3C and DS4.

DS-0
Digital Signal 0 (DS0) is a basic digital signalling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel.
The DS0 rate was introduced to carry a single digitized voice call. For a typical phone call, the audio sound is digitized at an 8 kHz sample rate using 8-bit pulse-code modulation for each of the 8000 samples per second. This resulted in a data rate of 64 kbit/s.

DS-3
A Digital Signal 3 (DS3) is a digital signal level 3 T-carrier. It may also be referred to as a T3 line.

* The data rate for this type of signal is 44.736 Mbit/s.
* This level of carrier can transport 28 DS1 level signals within its payload.
* This level of carrier can transport 672 DS0 level channels within its payload.
Used for The level of transport or circuit is mostly used between telephony carriers, both wired and wireless.

T-Carriers

In telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and Korea.
T-1 = runs at original 1.544 Kbit/s line rate

"T1" now means any data circuit that runs at the original 1.544 Mbit/s line rate. Originally the T1 format carried 24 pulse-code modulated, time-division multiplexed speech signals each encoded in 64 kbit/s streams, leaving 8 kbit/s of framing information which facilitates the synchronization and demultiplexing at the receiver. T2 and T3 circuit channels carry multiple T1 channels multiplexed, resulting in transmission rates of 6.312 and 44.736 Mbit/s, respectively.

E-Carriers

In digital telecommunications, where a single physical wire pair can be used to carry many simultaneous voice conversations, worldwide standards have been created and deployed. The European Conference of Postal and Telecommunications Administrations (CEPT) originally standardized the E-carrier system, which revised and improved the earlier American T-carrier technology, and this has now been adopted by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T).

E-1 = 2.048 Mbit/sec

An E1 link operates over two separate sets of wires, usually twisted pair cable. A nominal 3 Volt peak signal is encoded with pulses using a method that avoids long periods without polarity changes. The line data rate is 2.048 Mbit/s (full duplex, i.e. 2.048 Mbit/s downstream and 2.048 Mbit/s upstream) which is split into 32 timeslots, each being allocated 8 bits in turn. Thus each timeslot sends and receives an 8-bit sample 8000 times per second (8 x 8000 x 32 = 2,048,000). This is ideal for voice telephone calls where the voice is sampled into an 8 bit number at that data rate and reconstructed at the other end.