2. Group Member
Shahadat Hossain 131-15-2313
Sakhawat Hossain 131-15-2406
Mahmud Ahmed 131-15-2404
Din Islam 131-15-2243
Ibrahim Faisal 131-15-2262
Alamin Khan 131-15-2412
3. Digital Signal Service
Telephone companies implement TDM through a hierarchy of digital
signals, called digital signal (DS) service or digital hierarchy.
5. Digital Signal 0
• Digital Signal 0 (DS0) is a basic digital signaling 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 modulationfor each of the 8000 samples per second. This resulted in
a data rate of 64 kbit/s.
• the DS0 rate may support twenty 2.4 kbit/s channels, ten 4.8 kbit/s channels, five
9.67 kbit/s channels, one 56 kbit/s channel, or one 64 kbit/s clear channel.
6. Digital Signal 1
• Digital Signal 1 (DS1, sometimes DS-1) is a T-carrier signaling scheme devised by Bell Labs.
• DS-I is a 1.544-Mbps service; 1.544 Mbps is 24 times 64 kbps plus 8 kbps of overhead.
• It can be used as a single service for 1.544-Mbps transmissions, or it can be used to
multiplex 24 DS-O channels or to carry any other combination desired by the user that can
fit within its 1.544-Mbps capacity.
7. Digital Signal 2
• DS-2 is a 6.312-Mbps service; 6.312 Mbps is 96 times 64 kbps plus 168 kbps
of overhead.
• It can be used as a single service for 6.312-Mbps transmissions; or it can be
used to multiplex 4 DS-l channels, 96 DS-O channels, or a combination of
these service types.
8. Digital Signal 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 (45 Mb).
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.[1]
Such circuits are the usual kind between telephony carriers, both wired and wireless,
and typically by OC1[citation needed] optical connections.
9. DS3 pricing
DS3 service is provided to businesses in the United States through incumbent
local exchange carrier and competitive local exchange carrier communication
providers. The price, much like a T1 (or DS1) line, has two primary
components: the loop (which is distance-sensitive) and the port (or the price
the carrier charges to access the internet through their proprietary network).
10. Digital Signal 4
• DS-4 is a 274. 176-Mbps service; 274.176 is 4032 times 64 kbps plus 16.128
Mbps of overhead.
• It can be used to multiplex 6 DS-3 channels, 42 DS-2 channels, 168 DS-l
channels, 4032 DS-O channels, or a combination of these service types.
11. T Lines
• DS-O, DS-l, and so on are the names of services.
• To implement those services, the telephonecompanies use T lines (T-l to T-4).
• These are lines with capacities preciselymatched to the data rates of the DS-l to DS-
4 services.
• only T-land T-3 lines are commercially available.
• DS-O is not actually offered as a service, but it has been defined as a basis for
reference purposes
