User Guide

NPL-3 Company confidential
System Module and User Interface CCS Technical Documentation
Page 32 ãNokia Corporation. Issue 1 3/03
Int comparator output to change state, in this case from 0 to 1. The button can be used
for answering incoming calls but not to initiate outgoing calls.
Figure 9: External microphone connection
External Earphone Connections
Headset implementation uses separate microphone and earpiece signals. The accessory is
detected by the HeadInt signal when the plug is inserted (see section ACI, Accessory
Control Interface).
Figure 10: External Earphone & IHF Connections
When the accessory is inserted and the microphone path is biased the HookInt signal
decreases to 1.8V due to the microphone bias current flowing through the resistor. When
the button is pressed the microphone signals are connected together, and the HookInt
input will get half of micbias dc value 1.1 V. This change in DC level will cause the Hook-
Int comparator output to change state, in this case from 0 to 1. The button can be used
for answering incoming calls but not to initiate outgoing calls.
UEM
MICB2
MIC2P
MIC2N
HookInt
EMC/ESD
Com
p
onents
XMICP
XMICN
UEM
XEAR
MIC3P
MIC3N
EMC/ESD
Components
Rout+
Rout-
Lout+
Lout-
SPKRout+
SPKRout-
PhoneIN
(IHF)
Rin
Lin
Audio
Amplifier
VAFR
VAFL
FM Radio
PhoneIN (HS)
IHF Speaker
Audio amplifier
(IHS)