Alcatel MainStreet 2902, Manual

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19 — X.21 and V.35 DCMs
19-10 2902 MainStreet Technical Practices
90-2906-01 May 2002
Figure 19-2 Transmit and receive clocks
The two parameters for configuring clocking for synchronous transmissions are:
•
transmit clock source
•
type of synchronous clocking
Transmit clock source
When the device mode is synchronous, the clocking source between X.21 or V.35
DCM and the attached data device is selectable.
The transmit clock can be supplied by:
•
the attached device (EXTERNAL)
•
the data circuit to which the device is attached (INTERNAL)
•
a remote source (SLAVE) (default)
How this parameter is set depends on whether the circuit is in DCE or DTE mode.
Table 19-2 gives the transmit clock options for the DTE and DCE modes.
Table 19-2 X.21 and V.35 DCM clock sources
Transmit data
Receive data
DTE
data
device
DCE
data
device
Transmit clock
Receive clock
1535
Gender of
circuit Clocking
source Meaning
X.21 circuit
DCE and
DTE Slave The circuit extracts the transmit clock from the data stream.
V.35 circuit
DCE Internal A baud rate generator on the DCM provides the transmit clock.
The baud rate generator is locked to the system timing.
DTE Internal A baud rate generator on the DCM provides the transmit clock.
The baud rate generator is locked to the system timing.
External The user equipment provides the transmit clock.
Slave The circuit extracts the transmit clock from the data stream.