2.5mm jack curly clable with Plx QD "Works with Ciso SPA Series and other Cordless phones with 2,5mm Standard Headset Port.(3 poles with 2 black bands), No Smart phone use. Works with Grandstream ...

While 2.5mm was the original standard for phone headsets, the slightly larger 3.5mm size is standard for music headphones and is now the more common size on phones. See: Headphone Jack (3.5mm ...

If other headphones are unavailable, connect your wired headset to another device, such as your mobile phone. Clean the audio jack. A dirty audio jack cannot make proper contact with the wired ...