CLEAR SOUNDS - Alternative Model CLS-CS-A55 - 793537301008 Amplification up to 50dB; Caller ID / Call waiting with Caller ID UltraClear tone control to shape both high and low frequencies; Large Caller ID display Vibrating alert in handset and extra loud ringer in base and handset; Amplified 2.5 mm headset jack; Jack for Optional Vibrating Pad Back lit key pad; Expandable up to 3 handsets Hearing aid compatible; Hearing aid compatible