User Manual

Exalt Communications, Inc.
Exalt i-Series Installation and Management Guide
5000001 32
2007-06-25
such as GPS. The timing source to the Exalt radios can be adjusted to match the other
radio system timing source mechanism.
Offset timing can also optimize timing intervals for repeaters and backbones. As the
distance of each link results in a unique factor for speed-of-light transmission of the radio
signal, a subsequent radio can be delayed in timing so that the overall synchronization of
radios is precisely maintained.
Offset timing can be adjusted in 1-ms intervals, from zero to the radio’s frame length
setting. For example, if using a 2-ms frame length, the offset timing can be set from zero
up to 1999 ms.
Note: Offset timing is not supported in all models at the time of this
writing. Consult your Exalt representative for details.
When Sync is Lost
If the primary sync source (for example, the sync source radio or GPS source) signal is
lost due to equipment failure, a disconnected sync cable, or other conditions, the first
radio in the daisy-chain configuration set to AUTO SYNC resumes the sync function for
the remaining connected radios.
If a radio is configured as SYNC RECIPIENT, transmission ceases if the sync signal
does not appear at the SYNC IN connector.
A radio running in AUTO SYNC (without the sync source) is said to be flywheeling. That
is, the clock is free-running off internal clocking and is no longer synchronized to any
source.
If the original sync source is restored to the flywheeling radio configuration, the
flywheeling radio attempts to synchronize to this signal without causing transmission
interruption. All interconnected radios receiving sync from the flywheeling radio also
continue to operate without interruption.
When the flywheeling radio runs independently for long periods of time, the
synchronization signal can be too far outside of the capture range of the synchronization
loop, and portions of transmission frames can be lost during the re-synchronization
process. This condition is temporary and all interconnected radios re-synchronize to the
sync source, as necessary.
For GPS synchronization, the wiring inside the Exalt radio carries the GPS signal to the
next radio cabled in the system, even when power is removed from the SYNC SOURCE
radio or during radio failures. This provides redundancy for catastrophic failure of the
SYNC SOURCE and maintains GPS synchronization. If the GPS source is lost (for
example, due to failure of the GPS unit, a disconnected cable, or satellite blockage), the
AUTO SYNC radio resumes synchronization duties for all collocated radios.
LEDs
There are two LEDs on both the SYNC OUT and SYNC IN ports. Table 3 on page 39
describes the two SYNC IN and two SYNC OUT LEDs.