Here is the table of reference for the clock architecture on the Thor-2-PCMCIA:
------+----------------------+--------------------------+
Clock | Description | Clocksource parameter |
------+----------------------+--------------------------+
A | Clock extracted from |OTX_CLOCK_SOURCE_LOCAL_0 |
|incoming T1/E1 span 0 | |
------+----------------------+--------------------------+
B | Clock extracted from |OTX_CLOCK_SOURCE_LOCAL_1 |
|incoming T1/E1 span 1 | |
------+----------------------+--------------------------+
C | Onboard free running |OTX_CLOCK_SOURCE_INTERNAL |
| Oscillator | |
------+----------------------+--------------------------+

Clock D refers to an external 16.384 MHz clock. On the Thor-2-PCMCIA board all the internal TDM data highways and the all the devices processing TDM data are synchronized to one clock reference. The clock reference can be derived from multiple sources and then switched to all the devices. In the event that the clocking source is lost, Thor-2-PCMCIA will automatically switch to a backup clocking source. For example, if clocking is derived from an incoming T1/E1 span(Li 0), and the span experiences Loss of Signal (LOS), the clocking source is automatically switched to the internal oscillator.