ProTek Devices, based in Tempe, Arizona USA, is a manufacturer of Transient Voltage Suppression (TVS) products designed specifically for the protection of electronic systems from the destructive effects of lightning, electrostatic discharge (ESD), EMI/RFI and inductive switching.
With over 25 years of engineering and manufacturing experience, ProTek offers application specific protection solutions for any type of electronic equipment or system.
http://www.protekdevices.com

The SEMITEC Corporation was established 1958 in Tokyo, Japan. The company offers a bright range of products in their portfolio: thermistors (NTC), thermistor sensors, power thermistors, infrared sensors, thermopiles, surge absorber (VRD + Zenamiv MOV) and their world wide well-known and high quality current regulative diodes (CRD).
SEMITEC brand CRDs have been considered top class regarding their high reliability.
http://www.semitec.co.jp/english/

SFI Electronics Technology Inc., based in Taipei Taiwan, is a professional manufacturer of a full range of advanced multi-layer varistors (SMD varistors) in the size 0201 to 4032.
SFI has the largest production capability of MLVs in the world market and offers other product lines of the over voltage protection components, to supply customer with all kind of circuit protection devices for their applications.
The company is certified according ISO9001, ISO14001 and ISO/TS16949.
http://www.sfi.com.tw/index.php/en/

CT Micro International Corporation is a Customer Oriented and Technology Driven Company. It is dedicated to the design, marketing and sales of Optoelectronics and Discrete MOSFET products. With more than 15 years of products knowledge, CT Micro can help to realize any design right from component selection up to actual finished product implementation with minimum effort and time.
http://www.ct-micro.com