3Com S330 manual Received Plcp, CTX Timing Source-The CTX timing source for the DS3/E3 port

106CHAPTER 4: CONFIGURING PATHBUILDER S330/S310 MODULES, PORTS, AND APPLICATIONS

FEAC Loopback (DS3 only)—Enables or disables the system from responding to FEAC (Far-End Alarm Condition) loopback commands (loopback activate and deactivate FEAC codes) from the central office. FEAC is a DS3 overhead function that the service provider may use for establishing loopback for problem resolution of the network. The service provider uses FEAC codes to obtain downstream or upstream conditions of a DS3 network. When the FEAC Loopback option is enabled, the system responds to a loopback activate command by enabling the DS3 line loopback. The system removes the loopback automatically after 15 minutes or when it receives the deactivate command.

DS3 Timing Source (DS3 only)—The timing source for the DS3 transmit clock: system or loop. If you set the DS3 Timing Source to system at one end of the DS3 trunk, you must set it to loop at the other end.

System—Configures the port interface to use the system reference clock within the shelf as a reference for transmitting.

Loop—Configures the port interface to use the input port Rx clock as the timing source; timing is received from the service “loop.” Select this option if the DS3 UNI module is used for the network/carrier service termination, in which case the carrier (the service “loop”) typically provides the timing source.

E3 Timing Source (E3 only)—The timing source for the E3 transmit clock: system or loop. If you set the E3 Timing Source to system at one end of the E3 trunk, you must set it to loop at the other end.

System—Configures the port interface to use the system reference clock within the shelf as a reference for transmitting.

Loop—Configures the port interface to use the input port Rx clock as the timing source; timing is received from the service “loop.” Select this option if the E3 UNI module is used for the network/carrier service termination, in which case the carrier (the service “loop”) typically provides the timing source.

PLCP Timing Source (DS3 only)—The PLCP timing source for the DS3 port:

	System Clock—PLCP is timed from the internal 8kHz backplane clock.
	DS3 Timing—PLCP is timed from the 8kHz reference clock derived from
	the received PLCP.
	CTX Timing Source—The CTX timing source for the DS3/E3 port.
	DS3/E3 Rx Clock—Selects the DS3 or E3 Rx clock as the CTX timing source.
Configuring the Serial Configuring the serial interface involves the following tasks:
Interface	Configuring the serial port
■

■ Configuring the serial card