That little box is an adapter for RS232 communication analysis using a Yocto-RS232. If features two DB9 connectors, one male and one female, connected directly one to the other, which you can easily insert on a serial cable. The RJ12 connector allows you to connect it to a Yocto-RS232 using the RJ12 (6P6C) cable provided, so that the device can passively listen to the RS232 traffic.
With that adapter, your Yocto-RS232 can transcript the detail of RS232 communication, including the direction in which bytes have been sent. The adapter works like a straight cable (passive), it doesn't interfere with RS232 electric signals.
Hey guys when will we be able to buy this please need to do some RS232 Snooping hope to hear soon.