Plantronics P420 Calisto USB Speaker Phone UC Standard. Wherever the need arises to conduct hands-free, PC-based calls and web conferencing, the compact and portable Calisto 420 USB speakerphone caters to spontaneous collaboration. Advanced wideband audio, and a powerful 360-degree omni-directional microphone, transforms any workspace into a conference room, increasing productivity for everyone on the call. A convenient headphone jack accommodates private calls.