2 of the 4 handsets didn't ring on incoming calls. I checked the ringer off/on by pressing and holding down the star button all were set to on. However only the 2 phones that always rang gave a brief ring when the 'ringer on' msg was displayed the other 2 displayed the 'ringer on' msg but were silent. I prized the back off each of the silent phones and removed both batteries. 2/3 minutes later I put them back in and bingo every phone rings. Tech support told me to do this as it reboots the handset software. I don't have any special barring set up only the announcement setting.