The type of time interface that provides the time source
represented by this entry.
dsyp(1)
A DTM synchronization source (dsyp) represents a DTM
interface timing source and the synchronization control
information is distributed using the DTM Synchronization
Protocol (DSYP).
sqc(2)
A squelchable clock (sqc) represents a clock interface that
squelches its output to announce that it can not provide a
source at the expected quality level.
ssm(3)
An SSM clock (ssm) represents a clock interface that also
transports the Quality Level (QL) as a 4-bit Synchronization
Signal Marker (SSM).
internal(4)
An internal clock (internal) represents a holdover clock that
is internal to the node.