3Com's 3Com VCX V7000 Telephony Solution 5.0, Avaya's Avaya S8300 and S8700 Media Servers, Zultys' MX250 Enterprise Media Exchange, and Siemens' Siemens HiPath 4000 Real-Time IP System 2.0 are reviewed standards-based private branch exchanges (PBXs) that do not require users to purchase proprietary, costly phones. The four reviewed products all work on a standard Ethernet network with standard infrastructure and cabling. However, network infrastructure hardware has to be VoIP-ready to allow signaling protocols such as H.323 and Session Initiation Protocol (SIP) to travel the network. Firewalls and other security products also most be VoIP-ready or calls will not complete. 3Com VCX V7000 Telephony Solution 5.0, which is an application that runs on Linux on a standard Intel server can easily support hardware. The software is user-friendly and manageable. The management interface has an IT-savvy design, but the VCX V7000 will not scale for a large enterprise, and is an excellent solution for mid-sized companies. Avaya S8300 and S8700 Media Servers comes from a telephony leader, and have excellent features, management, scalability, setup, and overall value. The PBXs are designed for power and can be equipped to meet just about all requirements and can be expanded for very large enterprises. Design is telephony-savvy, but IT will still find management tools intuitive. Call setup protocols and voice streams are set up for encryption by default. MX250 Enterprise Media Exchange gets very high marks for features and setup and is a genuinely standards-based solution that demonstrates the excellence of SIP when correctly implemented. MX250 Enterprise Media Exchange is highly suitable for SMBs and works well with existing standards-based infrastructure. Any SIP device on the network is supported, and voice communications can be encrypted for better security. Siemens HiPath 4000 Real-Time IP System 2.0 is rated excellent for features, management, setup, and value. Siemens, an experienced telephony provider, made HiPath 4000 Real-Time System 2.0 configurable with redundant components and networked with other HiPath PBXs for fail-over. Conventional digital phones and IP phones are supported, based on options. The management interface is plain vanilla, but is very well documented and packed with tutorials and wizards.