Hey everyone, not new to forum but really don't get on here often. Issue is with the SV9100 8/32 button phones with the Plantronics CS540 connected via the APN-91 EHS cable. Have the NEC doc and know where the headset key goes, headset will work when initially installed however way too many complaints from customers that have issues with them. The user will push the connect button on the side of the headset and you will hear a click in the headset base but no dial tone over the headset, phone reset clears problem. We have shotgunned the install for some customers, phone, headset and EHS cable and won't hear back from them again however as stated way too many customers with the same problem. NTAC states they are unaware of the issue. Plantronics tech support said to use the APD-80 which of course only works with the IP sets. When using the APD-80 on the digital phone you need a physical headset button to push like a wired headset to make them work. Anyone have a definitive solution to this problem? Thanks in advance for your time.