Nokia NSB-7 Series Service Manual page 90

NSB-7
UI Module
Analog audio accessory detection
In XERP signal there is a 100 kΩ pull-up and 33k pull-down in the transceiver for Head-
Det. The HeadDet is pulled up when an accessory is connected, and pulled down when
disconnected. To get HeadDet working properly the system connector must be assembled
otherwise the transceiver will assume that some accessory is connected. In XMICN signal
there is a 1.2 kΩ pull-down in the transceiver and serial 1.2 kΩ from AUXOUT to XMICP.
The XMICN is connected to the transistor which is then connected to the HookDet line
(in MAD).
External accessory notices powered-up phone by detecting voltage in HeadDet line.
Accessory connected
No accessory connected
Headset with a button switch pressed
Headset with a button switch released
Hands free (PPH-1)
') HookDet is used only for detect button in headset.
''') HeadDet is used only for detect that some accessory is connected into system connec-
tor.
NOTE: Charging must stop when the detection sequences are done! CCUT signal at high
stops charging.
Headset detection
The external headset device is connected to the headset connector, from which the sig-
nals are routed to COBBA headset microphone inputs and earphone outputs. In the
XMICN line there is a 1.0 kΩ pulldown in the transceiver. The microphone is a low resis-
tance pull-up compared to the transceiver pulldown.
When there is no call going, the AUXOUT is in high impedance state and the XMICN and
XMICP are pulled down. When a headset is connected, the XMICP is pulled up. The
switch inside the system connector is connected to the HeadDet line (in MAD), an inter-
rupt is given due to both connection and disconnection.
NOTE: If the headset is connected switch closed, the transceiver can not detect if the
headset or PPH-1 in power off mode is connected. When switch is released to open the
transceiver can not any more detect the headset without polling by SW.
Page 10
HookDet*)
High
Low
High
Low
ãNokia Mobile Phones Ltd.
PAMS Technical Documentation
HeadDet**) Notes
Low
High XEAR and XMIC loaded (dc)
High XEAR and XMIC loaded (dc)
High XMIC loaded (dc)
Issue 1 06/00