Symmetricom TimeHub 5500 System Manual

28 097-55501-01 Issue 6 – June 2003
1
TimeHub 5500 System Guide
had most recently been qualified by the clock card before it was
removed. The attempt will begin with the lowest numbered
input.
- If none of the inputs that had been most recently qualified are
available (due to LOS), Passthrough will select any other input
that is providing a signal. The selection attempt will start with
the lowest numbered input.
• For example, if inputs 1,3, and 4 had been qualified by the active
clock card and input 3 was the active reference just prior to
removal of the clock card:
- Input 3 will be the first choice. If it is not providing a signal then
- Input 1 will be the next choice since it had been qualified by the
clock and it is the lowest numbered such input. If it is not pro-
viding a signal then
- Input 4 will be the next choice since it had been qualified and is
the next lowest numbered such input. If Input 4 was selected
and it goes away, Passthrough will cycle through the set of pre-
viously qualified inputs, in case one has returned. If it is not
providing a signal then
- If none of the qualified inputs are available, Passthrough will
look on the remaining inputs for a signal. In this case, the only
remaining inputs would be 0 (the 5/10 MHz input) and input 2
(DS1 input). Starting with 0, if an input is detected, it will be
selected as the active reference.
• If no timing input is providing a signal while in Passthrough, the
outputs will disable and Passthrough mode will end. Unlike clock
cards, which have the ability to provide holdover capability when
all timing inputs are removed (and thus maintain output timing),
the management card cannot provide holdover. Hence, outputs are
disabled if there is no timing input when in Passthrough mode.
There is a lamp on the management card that will illuminate if Passthrough
mode becomes active. An automatic message is also provided on both
communication ports whenever Passthrough operation begins or ends.
Details of the passthrough capability depend upon the firmware and
hardware versions of the management (090-55542-01), clock (090-5551x-
xx), and expansion controller (090-55545-01) cards. See note at end of this
section for how to check firmware and hardware versions.
If either the management or clock cards contain firmware prior to 4315B or
have hardware version A, then the passthrough capability will be as follows:

Symmetricom TimeHub 5500 Specifications

General

Brand	Symmetricom
Model	TimeHub 5500
Category	Data Loggers
Language	English