This is the connector schema for the pre-F4 interphone made by several manufactures, by example Blueant, Cell Line, interphone.
All they have keyhole form.
|5||Mic-/Chg-||Microphone - and Charger -|
The speaker is a 8 Ohms 3 Wats. the microphone is a little condenser microphone with a 0.1 pico farads and a diode soldered between the + and - terminals.