Model: ES336/ES56 Data/Fax/Voice Modem
Operating System: Windows 95 & Windows 98 (Note: might work with other versions of this os.)
ESS ES56T-X Data Fax Voice Modem
with both Windows 95 and Windows 98, and both worked fine. The first PC it was in was running Windows 95 with a 233 cyrix, and this PC has Windows 98 and a Pentium II Celeron 400....