Specifications:

• 110V AC to 220V AC or 220V AC to 110V AC
• Heavy Duty Transformer for safety and reliability
• ON/OFF switch with indicator light
• Universal output receptacles (will accept European 2 round pin plug, North America 2 flat pin and 3 prong plug
• The transformer weighs 22 lbs
• It measures 8.25" X 7.2" X 5.75"

Safety Features Include:

• Built-in (non-detachable power cord with strain relief)
• Fused Protection
• Safety polarized input switch (100V AC, 200V AC, 220V AC and 240V AC)
• Non slip rubber feet
•  
       -rubber feet for non-skid and isolated from ground.
       -standard US 3-prong plug input, 2 round pin adaptor is included.
       -universal output receptacles on both 110 and 220VAC (will accept 2 flat pin, 2 round pin, 3 prong US and Australia right angle 2 flat pin.
       -on-off switch with built-in circuit breaker,
       -white housing to fit in any decor.
       -90 days Mfg. warranty.

primary and secondary are not isolated

The correct term(technical) for ST-series is Autoformer or Autotransformer.