Does anyone know what this thing does??

[cheese101]

https://www.ebay.co.uk/itm/FM-radio-rec ... 1508088650

[MC Spanner]

From what i can gather it seems to be an FM receiver with a relay which can either be operated when it receives a signal, or a signal carrying the appropriate RDS. Doubt it's intended as an STL of any kind, maybe lets you turn on an amplifier or something? The blurb implies it's designed to be compatible with EL-15H which is a transmitter. Best I can do sorry!
https://www.aliexpress.com/item/Digital ... 47742.html
https://www.aliexpress.com/item/15W-hi- ... 86000.html

[Albert H]

From the stuff on DX.com and Alibaba, it looks like it's a receiver which will operate the relay when one of 32 signals is received (coded 0 - 31). They call this "RDS" - it's NOT broadcast RDS like we know it. It appears to be sub-audio tones.....

It seems to be intended to burst into life when it receives the correct signal, operating the relay to enable an amplifier and receive the transmitter sending the right access code and feed it to the amplifier. It's probably intended for a Public Address system