Specially designed single-phase isolating transformers with high transient suppression and low noise level. Designed and tested according to norm EN61558-2-19. 
SDT transformers are electrostatically shielded and have output filters which protect systems from unwanted "noise" and high frequency voltages that can occur due to switching and loading on distribution lines. 
Designed to protect equipment that requires a low-noise voltage in order to work without problems e.g.: computer equipment, telephone-exchanges and audio equipment.