Really pleased with this purchase for a number of reasons.
1) It works - and responds immediately to the button press - unlike other cheap makes reviewed on Amazon.
2) There is a choice of sounds - most of them as daft as you like, but fun - and I may use some of the Christmas rings in December. As other reviewers have noted - no instructions, but not really necessary. Just plug in, press the little button on the side of the plug-in unit and it plays a ring - press again and it plays the next - etc. It sets itself on the last one you selected.
3) The traditional 'DING DONG' (which I favour) plays twice - as if the caller has rung twice - very useful if you have limited brain cells like myself. More chance to hear the ring.
4) It has a huge advantage over its competitors on the plug in unit. As you can see on the picture display, it does not rob you of a plug socket - vital in my house which has the bare minimum. You can plug others into the unit. Furthermore (and this was a surprise) it is slim enough NOT to overlap if you plug it into a double socket. You can still plug in to the socket next to it - not the case with other plug-ins and adaptors I have bought.
5) No volume control but (for me) just enough volume to hear but not to give you a coronary when it is set up in the room you most inhabit. My last doorbell was so loud my neighbour used to rush to her door!
6) VERY CHEAP - with advantages over other cheap doorbells. You could pay a lot more for one of the expensive bells advertised but ... guess what ... it will go 'ding dong' just the same.
7) It's white - unobtrusive both on my white doorframe and white wall sockets.
DING DONG, BABY! UNRESERVED RECOMMENDATION.