The TI-99 Peripheral Expansion Box (PEB) is a remarkable expansion enclosure for the TI-99 computers. It offers space for either a single full-height floppy drive, or two half-height 5.25" models, as well as expansion slots for other peripherals. So instead of having a TI-99 "train", with several sidecars attached, you can have a single PEB, connected with massive cable.

Viewing from the back, the power supply is on the right and on the left is the full height floppy bay. In the centre is a back plane with 8 expansion slots. One is taken up by the "Flex cable interface", which connects the PEB to the computer, and one by the floppy controller.

Each slot has a cutout in the back of the machine to pass cables and a light pipe to the front for an activity LED.

Aside from the top cover, the whole side and front of the case can also be removed, revealing the power supply.

The power supply consists mainly of a large transformer and a small board.

Cards:

Atronic Peripherie Interface card

Although I wasn't able to find much information about this card, it seems to be a dual RS232 interface made by the company Atronic.

TI Disk Controller

This is the standard Texas Instruments disk controller, who's main chip is the Western Digital FD1771 floppy disk controller.

TI Flex Cable Interface

Lastly, there is the Texas Instruments Flex Cable Interface, which is a simple card, who's job it is to interface everything with the TI99 computer.

Floppy drives

The floppy drives were immaculate, most likely because they still have their original shipping cards installed.

All that was needed to make them work perfectly again was to remove the old dried up grease and apply some new silicone grease and machine oil.