Which version of H.323 first standardized communication between PC-based telephones and public switched circuit networks?

Version 2 of H.323 is recognized for standardizing communication between PC-based telephones and public switched circuit networks. This version introduced important enhancements over its predecessor, particularly the integration of technology that allowed for seamless interoperability between different platforms. It laid the foundation for connectivity between packet-switched networks, like the Internet, and traditional circuit-switched networks, which are essential for enabling voice calls and video conferencing.

This version included significant advancements in signaling and control procedures, allowing for better quality of service (QoS) and the ability to handle a wide range of data types. The work done in Version 2 was crucial for pushing forward the concept of convergence in telecommunication systems, which brought together varied communication methods into unified systems.