Sigfox is a LPWA network using the free radio frequency to communicate. There radio frequencies are changing in the different zone (Europe, America, Asia…) When you are developing a device you need to test it but you are not authorized to use all these frequency from the country you are.
The Sigfox emulator is a solution for this : it allows to directly connect your device and analyze the transmission whatever the frequency you are using is. The Sigfox emulator kit is an SDR dongle with a Sigfox software for understanding, decoding the sigfox signals.
You can wire your transmitter to this receiver to not emit the signal over-the-air and legally use a non authorized frequency in your country. When you are using an authorized frequency you can simply communicate over the air.