To keep the SBC T1/E1 interface in sync with the PSTN, ensure the following:  

  • The Clock Source to set to Network.
  • The T1/E1 port connected to the PSTN must be selected as the Primary Clock Port.
  • A different T1/E1 port (if available) is selected and connected to the PSTN as the Secondary Clock Port (or set to None).

When there is no PSTN connection, SBC 1K/2K Clock Source must be configured for System and the device connected to SBC1k/2K should derive clock from SBC1K/2K.

The System Clock Source setting applies to the TDM interface, and has no relationship to the system time.

Configuring System Timing

To configure system timing using a network clock source:
  1. In the WebUI, click the Settings tab.

  2. In the left navigation pane, go to System > System Timing.

    Configure System Timing

Configuration - Field Definitions

Clock Source

Specifies the source of the systems transmit clock.

  • System: The built-in oscillator is used to transmit data over synchronous links. The system's internal clock can be modified by the system administrator, see Configuring the System Date and Time.
  • Network: The clock is derived from the data received from the peer devices on the network.

Primary Clock Port

Specifies the DS1 port from which the clock will be derived. This field is visible only if Network is specified as the Clock Source.

Secondary Clock Port

Specifies the DS1 port from which the clock will be derived. This field is visible only if Network is specified as the Clock Source.
The Secondary Clock Source is used only if the primary clock source is not of sufficient quality or becomes unavailable.

Status

Indicates the status of the current active clock.

If the primary clock source goes down for whatever reason, the system will attempt to switch to the secondary clock source. If a secondary clock source is not configured here, the Status field will display as Free Run (uses the internal clock).

Possible values:

Primary. Indicates the Primary Clock Port is used.

Secondary. Indicates the Secondary Clock Port is used (if the Primary Clock Port is down).

Free Run. When the Primary Clock Port is down and a Secondary Clock Port is not configured, this indicates the clock source is the internal system clock.