The True Call is a wonderful device if you are plagued with spam phone calls.  You can also ask callers to identify themselves before you answer, or give them a special code to get straight through.  It includes an answering machine.  It works really well.  It comes with full instructions and all original packing, including mains adapter and phone connection.  According to the manufacturer the True Call works "on standard analogue domestic telephone lines from all the main telephone providers, and on most digital lines (with the exception of Vodafone, Zen Internet and Community Fibre)."