This is a read-only text string holding the called party's phone number for an active trunk connection call over the ATM voice interface. An administrator monitoring active calls can use it to identify exactly which destination number a given call leg is dialing, which is useful when tracing a specific call through the gateway. For example, if a trunk call is stuck or dropped, checking this value against dial records would show whether the router captured a number like "5551234" or came up with a null string, meaning the called-number data simply wasn't available for that leg.