T1
Terms
T1 Frame
The T1 Frame is 24 DS0 timeslots + framing bit.
- AKA, a D4 Super Frame
SF — Super Frame
- 12 T1 frames
ESF — Extended Super Frame
- 24 T1 frames
Link Down
- On RX
- 175 contiguous pulse positions with no positive or negative polarity.
On TX
- Sends
yellow alarmFar End Alarm - Next device downstream gets a
blue alarm
This device marks the link as T1 LOS Loss of Signal.
T1 Clocking Types
| Command | Description |
|---|---|
clock source line | derive reference from external device. |
clock source internal | use local PLL for reference. |
network-clock-participate | join the TDM backplane of the router. |
network-clock-select | Tells the TDM backplane to use certain T1 as a reference clock, and share it. |
network-clock-select requires a T1 line to be in clock source line mode.
network-clock-participate is required for network-clock-select
Mainboard voice DSPs MUST use the backplane clock. They can’t opt out.
All network-clock-participate devices share the same clocking-domain.
T1 Clocking Information
T1 reads from RX and TX buffers at the clock rate. Slips are reported when data is read at the wrong clock. Sometimes it might sample the same bit twice, sometimes it might miss bits completely.