Applicable to shaver supply units, embodying one or more socket-outlets, together with a single phase air cooled isolating transformer, with a rated supply voltage not in excess of 250 V a.c., a rated output not less than 20 VA and not in excess of 50 VA, a rated output voltage not in excess of 250 V and a rated frequency not in excess of 500 Hz. Also applies to shaver transformers for embodiment into shaver supply units.