BRI Layer 1 States

In this inactive (powered-off) state, the TE is not transmitting and cannot detect the presence of any input signals. In the case of locally powered TEs which cannot detect the appearance/disappearance of power source 1 or 2, this state is entered when local power is not present. For TEs that can detect power source 1 or power source 2, this state is entered whenever loss of power (required to support all TEI functions) is detected, or when the absence of power from power source 1 or 2, whichever power source is used for determining the connection status, is detected.

This state is entered after the TE has been powered on but has not determined the type of signal (if any) that the TE is receiving. When in this state, a TE may go to a low-power consumption.

This is the deactivated state of the physical protocol. Neither the NT nor the TE is transmitting. When in this state, a TE may go to a low-power consumption mode.

When the TE is requested to initiate activation by means of a PH-ACTIVATE request primitive, it transmits a signal (INFO 1) and waits for a response from the NT

At the first receipt of any signal from the NT, the TE ceases to transmit INFO 1 and awaits identification of signal INFO 2 or INFO 4.

When the TE receives an activation signal (INFO 2) from the NT, it responds with a signal (INFO 3) and waits for normal frames (INFO 4) from the NT.

This is the normal active state with the protocol activated in both directions. Both the NT and TE are transmitting normal frames. State F7 is the only state where B- and D-channel contain operational data.

This is the condition when the TE has lost frame synchronization and is awaiting re-synchronization by receipt of INFO 2 or INFO 4 or deactivation by receipt of INFO 0.

In this deactivated state, the NT is not transmitting. When in this state, an NT may go to a low-power consumption mode.

In this partially active state, the NT sends INFO 2 while waiting for INFO 3. This state will be entered on request by higher layers, by means of a PH-ACTIVATE request primitive, or on the receipt of INFO 0 or lost framing while in the active state (G3). The choice to eventually deactivate is up to higher layers within the NT.

This is the normal active state where the NT and TE are active with INFO 4 and INFO 3, respectively. A deactivation may be initiated by the NT system management, by means of an MPH-DEACTIVATE request primitive, or the NT may be in the active state all the time, under non-fault conditions.

When the NT wishes to deactivate, it may wait for a timer to expire before returning to the deactivated state.