This selects which encapsulation translation is applied to this circuit's traffic when it crosses between Frame Relay and ATM, RFC1490 (native Frame Relay multiprotocol encapsulation, or no translation) versus RFC1483 (the ATM-native equivalent), which must match what the equipment on both ends of the circuit expects. An admin connecting Frame Relay CPE across an ATM backbone via interworking needs this set correctly, since a mismatch causes the far end to receive frames it can't correctly decode even though the circuit itself shows as up. For example, setting cktXlatFlag to rfc1483(1) on a Frame Relay-to-ATM interworking circuit ensures IP or bridged frames are translated into the RFC1483 format expected by an ATM-attached router at the far end.