Laboratory transformers, or laboratory autotransformers are devices that enable to adjust voltage in the range from 0 to 250 V. Such equipment is used when there is a need for off-standard voltage rather than original 220 V.

Laboratory transformers have manual controllers that need to be turned according to voltmeter indications to adjust the needed voltage.  Therefore, laboratory transformers are not automatic devices, unlike voltage stabilizers.

Actually laboratory transformers are voltage coefficients, which causes voltage alterations at the device input cause proportional alterations at the output.