Isolation Transformer often has symmetrical winding which is used to decouple 2 circuits. It incorporates a full metallic shielding (copper /aluminum) between primary & secondary winding
Isolation Transformers are being used to protect electronic & sensitive creative equipment such computer & peripherals medical instruments, digital machines & CNC M/C from the Excessive line voltage transient, spikes/surges which produced in the system. Apart from this, isolation Transformer also obstructs those disturbances that are generated by the noisy equipment from being injected into the power line i.e. it filters common mode noise usually an attenuation of approx. 30 db.