System Management
7750 SR OS Basic System Configuration Guide Page 373
Parameters ds1 esf — Specifies Extended Super Frame (ESF). This is a framing type used on DS1 circuits that
consists of 24 192-bit frames, The 193rd bit provides timing and other functions.
ds1 sf — Specifies Super Frame (SF), also called D4 framing. This is a common framing type used
on DS1 circuits. SF consists of 12 192-bit frames. The 193rd bit provides error checking and
other functions. ESF supersedes SF.
e1 pcm30crc — Specifies the pulse code modulation (PCM) type. PCM30CRC uses PCM to separate
the signal into 30 user channels with CRC protection.
e1 pcm31crc — Specifies the pulse code modulation (PCM) type. PCM31CRC uses PCM to separate
the signal into 31 user channels with CRC protection.
ref-order
Syntax ref-order first second [third]
no ref-order
Context config>system>sync-if-timing
Description The synchronous equipment timing subsystem can lock to different timing reference inputs, those
specified in the ref1, ref2 and bits command configuration. This command organizes the priority
order of the timing references.
If a reference source is disabled, then the clock from the next reference source as defined by ref-
order is used. If the reference sources are disabled, then clocking is derived from a local oscillator.
Note that if a sync-if-timing reference is linked to a source port that is operationally down, the port
will no longer be qualified as a valid reference.
On the 7750 SR7 and 7750 SR12, the bits input port on both the active CPM and standby CPM (if
present) are accessible by the active standby. Wherever bits appears in the ref-order, the order of the
two bits ports will be active CPM followed by standby CPM.
The no form of the command resets the reference order to the default values.
Default bits ref1 ref2
Parameters first — Specifies the first timing reference to use in the reference order sequence.
Values ref1, ref2, bits
second — Specifies the second timing reference to use in the reference order sequence.
Values ref1, ref2, bits
third — Specifies the third timing reference to use in the reference order sequence.
Values ref1, ref2, bits
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