[octanechicken] has a possible adapter solution that lets you plug ... to work with older Xbox 360 chat headsets having a male 2.5 mm plug. The photos on the instructable are still incorrect ...

Therefore most modern phones require a 3.5mm-to-2.5mm adaptor in order to connect to a TTY device. Either size can support stereo sound and/or a microphone, depending on the number of separate ...