CITEL was established in 1936 and has offices in the USA, Europe and China. CITEL manufacturing facilities are ISO 9002 approved. Many models are offered for T1/E1, RS232, RS422, RS423, RS485, ISDN, 56k/DDS, Leased lines, telephone lines; for COAXIAL cable and TWISTED pairs. CITEL is also one of the world's largest manufacturers of surge arrester gas tubes. They come in any voltage from 75V to 1500V. Some models are available in Surface Mount Technology.