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Synchronous Serial Overview
Figure 1-2
The PA-4T+ provides four synchronous serial ports, and each port supports full-duplex operations at T1
and E1 speeds.
Speed is controlled by three variables:
•
•
•
The CSU/DSU determines the maximum speed of the full-duplex port. No configuration is necessary. If
a CSU/DSU runs at a maximum speed of 1.55 Mbps (T1 speed), using only one port in the port adapter
will not make this CSU/DSU run at E2 speed. On the other hand, if a CSU/DSU is capable of
E2 speed (8 Mbps), this CSU/DSU will take the maximum bandwidth of the port adapter. To ensure this
speed, no other port can be used. If you use another port, the speed of the CSU/DSU capable of E2 speed
is reduced, because the port adapter shares the bandwidth between the two ports.
For running at speeds above 2 Mbps, the PA-H with appropriate DSU is a better choice.
Note
When two full-duplex ports are in use, the maximum speed for each is 4 Mbps. When four full-duplex
ports are in use, the maximum speed for each is 1.55 Mbps (T1) or 2.048 Mbps (E1).
Synchronous Serial Overview
The PA-4T+ provides four channel-independent, synchronous serial ports that support full-duplex
operation at T1 (1.544-Mbps) and E1 (2.048-Mbps) speeds. Each port supports any of the available
interface types:
•
•
•
•
EIA/TIA-232, which is the most common interface standard in the U.S., supports unbalanced circuits at
signal speeds up to 64 kbps. EIA/TIA-449, which supports balanced (EIA/TIA-422) and unbalanced
(EIA/TIA-423) transmissions, is a faster (up to 2 Mbps) version of EIA/TIA-232 that provides more
functions and supports transmissions over greater distances. The EIA/TIA-449 standard was intended to
replace EIA/TIA-232, but it was not widely adopted.
The EIA/TIA standards were referred to as recommended standards called RS-232 and RS-449 prior to
Note
their acceptance by the ANSI committee.
PA-4T+ Synchronous Serial Port Adapter Installation and Configuration
1-2
PA-4T Port Adapter—Faceplate View
The number of ports in use
The maximum speed allowed by the port adapter
The maximum speed of the attached CSU/DSU.
EIA/TIA-232
EIA/TIA-449
V.35, X.21
EIA-530
Chapter 1
Overview
OL-3561-04
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