Internal Microphone And Earpiece; External Audio Connections - Nokia Mobile Phones NSE-5 Series Service Manual

PAMS
Technical Documentation
The output for the internal earphone is a dual ended type output capable
of driving a dynamic type speaker. The output for the external accessory
and the headset is single ended with a dedicated signal ground SGND.
Input and output signal source selection and gain control is performed
inside the COBBA–GJP asic according to control messages from the
MAD2. Keypad tones, DTMF, and other audio tones are generated and
encoded by the MAD2 and transmitted to the COBBA–GJP for decoding.

Internal Microphone and Earpiece

The baseband supports three microphone inputs and two earphone
outputs. The inputs can be taken from an internal microphone, a headset
microphone or from an external microphone signal source. The
microphone signals from different sources are connected to separate
inputs to the COBBA_GJP asic. Inputs for the microphone signals are of a
differential type.

External Audio Connections

The external audio connections are presented in figure 16. A headset can
be connected directly to the system connector. The headset microphone
bias is supplied from COBBA AUXOUT output and fed to microphone
through XMIC line. The 330ohm resistor from SGND line to
AGNDprovides a return path for the bias current.
Issue 1 07/99
NSE–5
System Module
Page 2 – 31