This attribute records the results of the clock source test, indexed by
the clock source and the slot number of the card containing the bus
tap tested. Each entry contains one of the following values.
+: the bus tap was able to receive clock signals from the clock
source
X: the bus tap was unable to receive clock signals from the clock
source
.: the bus tap was not tested against the clock source
The bus test terminates automatically if a failure is detected
involving the active control processor (CP) clock source.