Please have a look at the relevant links for user manuals and installation guides for different Telephone Adaptors (VoIP):
HandyTone HT488 Telephone Adaptor (Analog)
HandyTone HT486 Telephone Adaptor (Analog)
HandyTone HT386 Telephone Adaptor (Analog)
HandyTone HT286 Telephone Adaptor (Analog)