APDU Scanner Kits
This is when you wish to have the logger emulating a smart card by having the PC software talking to the external card reader.
In this mode you can then take a log of the communication.
Now in this mode the logger does not do any talking at all, when instead it only listens to the smart card and external card reader talking to each other.
This communication can then be logged for analysis.
When you don't care about logging, then in this mode you can simply emulate the smart card (useful when building a decoder).
Or if the logger / emulator has its own card slot, and an external power option, then you can emulate being the card reader. You can also power these models through the card reader.