When were socket outlets introduced? Did early wiring have outlets or were all lamps hardwired?
The reason I'm asking is that I visited a 19th century house with the original light switches and light fixtures still in use. The switches weren't a standard design but purpose built to fit the place were mounted, e.g. a door frame. Very neat. I couldn't however find any socket outlets except in the bedroom: One (single) on each side of the bed. Both appeared to be of the usual two pin type. I wondered if this might have been a somewhat later addition.
I will try to get permission to photo the system and to open the odd box and switch in August. All Swedes - except me - are on vacation in July.