DS3 Definitions
DSL 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.
- 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.
Cabling
DS3 interconnect cables
must be made with true 75 ohm cable and connectors. Cables or connectors which
are 50 ohm or which significantly deviate from 75 ohms will result in reflections
which will lower the performance of the connection, possibly to the point of
it not working. Bellcore standard GR-139-CORE defines type 734 and 735 cables
for this application. Due to losses, there are differing distance limitations
for each type of cable. 734 has a larger center conductor and insulator for
lower losses for a given distance. The BNC connectors are also very important
as are the crimping and cable stripping tools used to install them. Trompeter,
Cannon, Amphenol, Kings, Canare are some of the true 75 ohm connectors known
to work. RG6 cable will also work, though it does not meet telephony technical
standards.
T-carrier
A digital transmission service from a common carrier. Although developed
in the 1960s and used internally, AT&T introduced it as a communications
product to the public in 1983. Initially used for voice, its use for data
grew steadily, and T1 and T3 lines are widely used to create point-to-point
private data networks. T-carrier lines use four wire cables. One pair is
used to transmit; the other to receive.
The cost of the lines is generally
based on the length of the circuit. Thus, it is the customer's responsibility
to utilize the lines efficiently. Multiple lower-speed channels can be multiplexed
onto a T-carrier line and demultiplexed (split back out) at the other end.
Some multiplexors can analyze the traffic load and vary channel speeds for
optimum transmission. See DS, DSU/CSU and inverse multiplexor. |
