I decided to do a lil` post about PlayStation names. Feel free to correct (&/or critique) me.
PlayStation - the original name for the Playstation and now the name for the gaming section of Sony.
PS1 - this
should be the name for the original Playstation now.?
PSone - the name for the revised model of the original Playstation.
PocketStation - a little handheld that never made it to the states. It looked alot like Sega's VMU and as I understand it worked similarly to it too, except for the whole connecting to your controller deal. It was for use with the PS1
PS2 - (PlayStation 2) the second generation of Playstation.
PSX - originally used by fans as a name to refer to the PS1 Sony decided that it would be a good name for the multimedia version of their PS2, this isn't available in the US.
PSP - (PlayStation Portable) Sony's new handheld currently in development. Supposedly a portable version of the Playstation(PS1), hence the name.
PStwo - if Sony make's a revised model of the PS2 you can bet this is what they'll call it, as a matter of fact I think I read somewhere that Sony recently registered that name, as a matterer of facts I think it was on PGC

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Like I said please post comments and corrections, I'm basically just posting this for the names of the systems but feel free to post other basic info on the systems.