This read-only AtmAddress reports the Calling Party Subaddress of the call, an additional addressing field beyond the main calling address used to identify a specific sub-endpoint. An administrator reads this when a calling ATM address alone is not specific enough to distinguish which sub-endpoint behind that address originated the call. For example, on a multi-endpoint terminal adapter sharing one calling address, cwspCallCallingSubAddr lets an operator identify precisely which sub-endpoint placed a particular call.