Viking RG-10A Ring Booster Designed to increase the ringing power of an existing telephone line, PABX extension, FXS port, IP phone system analog port or any other telecom device which provides ringing Duplicates the incoming ring frequency and cadence allowing it to be compatible with custom ringing features Capable of ringing twelve standard (1 REN) telephones and does not affect normal operation of the telephone line or features provided by the phone company, such as caller ID and call waiting Multiple RG-10As may be used for even higher drive output