Avaya Definity TN792 Duplication Interface (Refurbished)Avaya Definity TN792 Duplication Interface. More Information In high and critical reliability R7 or later si systems, copies contents of memory from the primary Switch Processing Element (SPE) to a standby SPE, so that the latter can take over immediately when the former fails Two TN792 circuit packs required, one for primary control carrier and one for standby You can replace TN772 duplication interfaces with TN792s, but you must replace them in