Pinout 
NOKIA SPECIAL at the cellular phone.
|  Pin  | 
 Name    | 
 Description
 | 
|  1    | 
 GND     | 
 Charger/System Ground
 | 
|  2    | 
 V_OUT   | 
 Accessory Output Supply. (3.4V...10V - 50mA)
 | 
|  3    | 
 XMIC    | 
 External Microphone Input and Accessory Identification
 | 
|  4    | 
 EXT_RF  | 
 External RF Control Input
 | 
|  5    | 
 TX      | 
 FBUS Transmit
 | 
|  6    | 
 MBUS    | 
 Serial Control Bus
 | 
|  7    | 
 BENA    | 
 Not Connected
 | 
|  8    | 
 SGND    | 
 Signal Ground
 | 
|  9    | 
 XEAR    | 
 External Speaker and Mute Control
 | 
|  10   | 
 Hook    | 
 Hook Signal
 | 
|  11   | 
 RX      | 
 FBUS Receive
 | 
|  12   | 
 V_IN    | 
 Charging Supply Voltage (Max 16V)
 | 
  XMIC: External Microphone Input and Accessory Identification 
|  U low   | 
 U high  | 
 Description
 | 
|  1.15 V  | 
 1.4 V   | 
 Compact Handsfree Unit Connected
 | 
|  1.7 V   | 
 2.05    | 
 Headset Adapter Connected
 | 
|  2.22 V  | 
 2.56 V  | 
 Infra Red Link Conneceted
 | 
  EXT_RF: External RF Control Input 
|  U low  | 
 U high  | 
 Description
 | 
|  0.0 V  | 
 0.5 V   | 
 External RF in use
 | 
|  2.4 V  | 
 3.2 V   | 
 Internal Antenna in use
 | 
  MBUS: Serial Control Bus 
|  U low  | 
 U high  | 
 Description
 | 
|  0.0 V  | 
 0.5 V   | 
 Logic Low Level
 | 
|  2.4 V  | 
 3.2 V   | 
 Logic High Level
 | 
  XEAR: External Speaker and Mute Control 
|  U low  | 
 U high  | 
 Description
 | 
|  0.0 V  | 
 0.5 V   | 
 Mute ON (HF Speaker Mute)
 | 
|  1.0 V  | 
 1.7 V   | 
 Mute OFF (HF Speaker Active)
 | 
  Hook: Hook Signal 
|  U low  | 
 U high  | 
 Description
 | 
|  0.0 V  | 
 0.5 V   | 
 Hook Off (Handset in Use)
 | 
|  2.4 V  | 
 3.2 V   | 
 Hook On (Handset in Use)
 | 
  Contributions 
  Sources