Each teleporter has 2 radios and there is 1 at the main frame. Hit X to play the recording.

MF = to the left of the stairs to the Thompson room there is some barrels. The radio is by them on the left.

TP A1 = Open ramp side door, open next door. Where you would make a left to buy the Trenchgun, look right and up instead; there is a little shelf with the corner of a radio sticking out (just right and above the ? box location there).

TP A2 = Looking at the teleporter after you open the door, there are 2 cremation ovens, the one on the right is open and the radio is in there.

TP B1 = Open the Thompson room stairs, make a right. While looking at the 750 point door, the radio is on the left on a slanted file cabinet.

TP B2 = open that 750 point door, the radio is on a ladder going down the cooling tank on the left (this is hard to see and activate).

TP C1 = On the bookcase at the bottom of the stairs that lead to the balcony, you can't miss it.

TP C2 = At the end of the tunnel, behind some boards (where you fall down from QR).

Also, in addition to the other paperwork mentioned in other posts here, there is a open book that you can read a page of; get the PTRS, open the 'ramp side' (Trenchgun side) of the starting area, go to the window to the left, lay down and peer through the hole in the sandbags, scope in and read.