TDB Start-up Card
The TDB Start-up Card is a special peripheral made for rudimentary debugging on DTL-H models. In it's contents, it has the TDB software installed as a system update, so it would auto-boot on every DTL-H model except DTL-H10000 and DTL-H3x0xx.
Purpose
The program's main purpose is to set up the TIF, a network "clone" of the PIF (the hardware interface that serves as bridge between the PC and the PS2 inside the DTL-T models). This allows the DSNET toolset to comunicate with the TDB Start-up card from a PC via a network cable. The TDB Start-up card also includes an EE Kernel replacement to reimplement the EE thread track extension.
Limitations
It is incapable of any form of debugging on the IOP. For this purpose, the DTL-T models are required instead. The card has a different MagicGate keystore, so it can only be authenticated on DTL-H models.
More information
There isn't much additional information about this card on the internet. However, an in depth explanation of it's behavior and capabilities can be obtained by taking a look at the RDB Start-Up Card, a homebrew clone made for retail models.