On release 7 or later, high and critical reliability, copies contents of memory from the primary SPE to a standby SPE. The latter can then take over immediately when the former fails. The TN792 circuit packs require two of them, one for primary control carrier and one for standby. This model can be replaced with TN772 duplication interfaces with TN792s, but they must be replaced in pairs. The TN722 does not communicate with a TN792.
Copies contents of memory from the primary SPE to a standby SPE