The Scott-T transformer was used to run 2-phase equipment from a 3-phase source. Older power distribution systems (and equipment) were 2-phase. An isolation transformer usually has the same input and output voltages (120:120, 240:240, etc) and is used to isolate the source from the load. Isolation Transformers are used in medical equipment, for instance, to prevent a patient hooked up to a monitor from being electrocuted during an electrical fault.