Nokia NSB-7 Series Service Manual page 91

NSB-7
PAMS Technical Documentation UI Module
Headset switch detection
In the XMICN line there is a 1.0 kΩ pulldown in the transceiver. The microphone is a low
resistance pull-up compared to the transceiver pulldown. When a remote control switch
is open, there is a capacitor in parallel with the microphone, so the XMICN is pulled up
and HookDet pulled closed, the XMICN is pulled down via the microphone and HookDet
is pulled up. So both pressing and releasing of the button gives an interrupt when AUX-
OUT is set to 2.1 V.
PPH-1 detection
The external Plug and Play PPH-1 device is connected to the system connector, from
which the signals are routed to COBBA headset microphone inputs and earphone out-
puts. In the XMICN line there is a 1.0 kΩ pull-down in the transceiver. The PPH-1 has a
low resistance pull-up compared to the transceiver pull-down. When there is no call
going, the AUXOUT is in high impedance state and the XMICN and XMICP is pulled down.
When a powered PPH-1 is connected, the XMICP is pulled up. The switch inside the sys-
tem connector is connected to the HeadDet line (in MAD), an interrupt is given due to
both connection and disconnection.
The PPH-1 device has two operating mode devices with external microphone and with-
out external microphone. When internal microphone is used the detection signal (EAD) is
higher than when external microphone is used.
NOTE I: If the PPH-1 is connected in power off mode, the transceiver can not detect if
the device is a headset or a PPH-1 connected. When PPH-1 is powered on it is possible to
detect when case of PPH-1.
NOTE II: If the external microphone is connected from or disconnected to PPH-1 it is not
possible for the transceiver to detect when that happens.
Internal audio connections
The speech coding functions are performed by the DSP in the MAD2 and the coded
speech blocks are transferred to the COBBA for digital to analog conversion, down link
direction. In the up link direction the PCM coded speech blocks are read from the COBBA
by the DSP.
Issue 1 06/00 ãNokia Mobile Phones Ltd. Page 11