How does the pc sync work?

Can someone explain to me how the pc sync port should be used? Can it transmit ttl? Can it be used together with the hotshoe? (like one flash on the hotshoe and another with the pc sync?) can a remote trigger be triggered by the pc sync?

It's a bit of a throwback to earlier times Seb, but I believe it still has it's uses.

As I understand it (haven't used one myself, and it predates the Pentax DSLRs by many many years) it provides a basic flash trigger signal, only up to the max sync speed. No TTL data, so only for triggering flashes with their own locally set manual power. A radio trigger could take the signal if it had the required input and then do it's thing ......

I am sure that there will be more experienced flash users here who have used it in practice and can correct anything I have got wrong.

Basically it pre-dates the hot shoe. Originally the accessory shoe had no electrical contacts, its purpose was to hold a light meter, range finder or flash etc. So the pc sync socket gives those non hotshoe flashes an electrical contact.
They'll still get used for some lighting systems such as ring flashes.

Seb asks a good question about whether the hotshoe and PC port can be used together on our modern DSLRs .... Has anyone tried using a flash on the hotshoe and something from the PC port simultaneously?

yeah thanks, I have way too many remote triggers at the moment and I would like to use some basic ones with the pc sync, if it can work with the hotshoe one. The idea would be to buy an external hotshoe that can be attached to the pc sync port and put an extra trigger there

I never reply to this, but the silly setup works fine. I have a aputure master on top of a cactus on the hot shoe and a godot remote trigger with the pc sync cord.