Compatible with fax machines and modem speeds up to 28.8 kbps- Precise dial tone 32V DC talk battery- Switch selectable ring cadence- Provides CPC breaks after hang-up on either port- Switch selectable audio attenuation- Provides 2 seconds of precise dial tone after off-hook- Provides ring back signal to calling device- One or two way ring down capability- Jumber selectable ring count- Ring down and dial tone off mode ideal for prison phone communications, etc.