Board Thread:The Panopticon/@comment-4139960-20131112180414/@comment-26975268-20131113153815

Okay, first of all, "dimension cannon" is the only non-conjectural title between them. Except it's notably different to the other two/one:
 * Basically, we've been building this, er, this travel machine, this, this er, dimension cannon, so I could. Well, so I could [..] come back.

So the dimension cannon was clearly built AFTER Doomsday. This is actually not reflected on the device's page, which treats it the same as the others. The BTS note at the bottom of dimensional transporter actually raises a good point – they have different physics because they're different devices.

As far as medallion and dimensional transporter, they seem to both be the same device used in Doomsday. This one, according to Pete, was developed by Pete's World's Torchwood. It could only transport one person at a time according to Mickey – though managed to do just fine when Pete rescued Rose at the end.

Clearly, between Doomsday and The Stolen Earth (welll, Turn Left), Torchwood tried to create another device – the dimension cannon – that would work in the new circumstances. It didn't work at first until Davros began to break the barriers between worlds with his Reality Bomb.

So we have two distinct devices here, even if one was based on the other. Basically, medallion and dimensional transporter need to be merged, and dimension cannon needs to be rewritten to reflect that it was NOT the device used in Doomsday.