SEI Telephony Products
About SEI
SEI Telephony Products
Founded in 1977, SEI manufactures DC (direct current output) critical power systems and customer-premises power equipment (CPE) for industrial users, wireless, telephone service providers, and the military. SEI is located in a 24,000 sq. ft modern manufacturing facility in Frederick, Maryland. SEI has shipped over 20,000 DC critical power systems to customers around the world. SEI products are proudly made in the USA.

SEI Products

We build DC uninterruptible power systems (UPS) that provide 48 Vdc and 24 Vdc battery backed-up power. These 'power plant in a box' systems have output power distribution modules and options that facilitate use in a wide variety of applications. Batteries provide holdover time from 20 minutes to 8 hours. Find out more about SEI's DC UPSs.

SEI also builds DC powering systems and Network Termination Units (NT1s). These provide power and computer interfaces for Digital Centrex telephones, which employ ISDN as its protocol. SEI is the largest supplier of these products in North America. Find out more about SEI's line of ISDN products.

Our Power over Ethernet (PoE) midspan injectors provide power for voice and data over Ethernet for IP telephones and devices that require power to be delivered over a LAN. SEI participated in the IEEE task force that formulated the 802.3af standard for Power over Ethernet, and has engineered power and battery backup solutions for this technology. Find out more about SEI's Ethernet power solutions.

For order information or technical support call us at
or email us using our Contact Us form
> LINKS - Click for more information
DC-UPS Products
ISDN Power Products
Midspan Injectors for PoE

System Engineering International, Inc. • 5115 Pegasus Court • Suite Q • Frederick, MD 21704
Voice: (301) 694-9601 • Fax: (301) 694-9608 • Email:

Home | About SEI | DC UPS | PoE Midspans | ISDN Products | Power Services | Contact Us | Support & Sales | Sitemap