Telecom Fans NMB Technologies Telecom Fans feature auto-restart or polarity protection and 700VAC dielectric withstand voltage. These NMB Technologies telecom fans feature 12VDC or 48VDC operating voltage and airflow ranging from 19.4CFM to 185CFM. Options include a metal casing that provides high reliability in high temperatures. The Telecom Fans operate at a temperature range of -10°C to +70°C. These fans are designed for use in telecom applications.