This portable Telephone Ringer Amplifier goes between your telephone set and the wall phone line to boost the volume of the ring. The RJ11 Telephone Ring Amplifier works wonders in pronouncing incoming calls particularly in noisy places. It helps the hearing-impaired, the heavy sleepers, and people who love wandering far from their phones. Connect it the telephone line, no other electrical power is needed. 2 RJ11 Socket. Need another adapter for UK buyers or others. Installation: Please connect the c and o line connector with ringer jack. The connector of the ringer connect with telephone.