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Dial Feature Card Ports
The TDM bus can be synchronized with any DFC cards. On the CT1/CE1 DFCs, each port receives the clock from the T1/E1
line. The CT3 DFC uses an M13 multiplexer to receive the DS1 clock. Each port on each DFC trunk slot has a default clock
priority. Also, clock priority is configurable through the dial-tdm-clock priority CLI command.
External Clock
The TDM bus can be synchronized with an external clock source that can be used as an additional network reference. If no
clocks are configured, the system uses a primary clock through a software-controlled default algorithm. If you want the external
T1/E1 clock (via the BITs interface) as the primary clock source, you must configure it using the dial-tdm-clock priority CLI
command; the external clock is never selected by default.
The BITs interface requires a T1 line composite clock reference set at 1.544 MHz and an E1 line composite clock reference set
at 2.048 MHz.
Free-Running Clock
If there is no good clocking source from a DFC card or an external clock source, then select the free-running clock from the
local oscillator using the dial-tdm-clock priority CLI command.
To configure the clock source and clock source priority used by the TDM bus, follow these steps:
Step1 Use the enable command and password to enter privileged EXEC mode. You are in privileged EXEC mode when the
prompt changes to Gateway#.
Gateway> enable
Password: password
Gateway#
Step2 Enter global configuration mode. You are in global configuration mode when the prompt changes to Gateway(config)#.
Gateway# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Gateway(config)#
Step3 Perform Step a or Step b, depending on your configuration:
a. Step a configures the CT1/CE DFC clock priority, trunk slot, and port that is providing the clocking source. Priority
range is defined as a value from 1 to 99. DFC slot is defined as a value from 1 to 7. DS1 port number controller is defined
as a value from 0 to 7.
Note DS1 port specifies T1 port.
Gateway(config)# dial-tdm-clock priority priority# {external | freerun | slot/ds1 port}
b. Step b configures the CT3 DFC clock priority, trunk slot, and port that is providing the clocking source. Priority range
is defined as a value from 1 to 99.
DFC slot is defined as a value from 1 to 7. DS3 port specifies the T3 port. DS1 port number controller is defined
as a value between 1 and 28.
Gateway(config)# dial-tdm-clock priority priority# {external | freerun | slot/ds3 port:ds1 port}
Step4 Return to privileged EXEC mode:
Gateway(config)# Ctrl-Z
Gateway#