External Microphone Connection; External Earphone Connection - Nokia RH-27 Series Technical Documentation Manual

CCS Technical Documentation

External Microphone Connection

The external microphone input is fully differential and lines are connected to the UEM
microphone input MIC2P/N. The UEM (MICB2) provides bias voltage. Microphone input
lines are ESD protected.
Creating a short circuit between the headset microphone signals generates the hook sig-
nal. When the accessory is not connected, the UEM resistor pulls up the HookInt signal.
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.
HookInt
MICB2
UEM
MIC2P
MIC2N

External Earphone Connection

Headset implementation uses separate microphone and earpiece signals. The accessory is
detected by the HeadInt signal when the plug is inserted.
FM Radio
VAFR
VAFL
MIC3P
UEM
MIC3N
XEAR
Issue 1 11/2003
Figure 11: External microphone connection
Audio Amplifier
Figure 12: External earphone and IHF connections
© 2003 Nokia Corporation
EMC/ESD
Rin
Rout+
Lin
Rout-
Lout+
Lout-
SPKRout+
SPKRout -
PhoneIN (HS)
PhoneIN (IHF)
Confidential
RH-27
System Module
XMICP
XMICN
IHF Speaker
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