SYSTEM CONNECTOR INTERFACE
30
LZT 123 8020 R1A
5.7 Analogue
Audio
Pin Signal
Dir
Description
57
AFMS
O
Audio from mobile station
59
ATMS
I
Audio to mobile station
60
AGND
-
Ground (return) for analogue audio
ATMS is the audio input, and AFMS is the audio output, of the
radio device. These signals can be used in car kit mode.
There are three factory-set audio profiles:
•
portable
handsfree
•
handset
•
car
kit
Portable handsfree is the factory-set default profile. The
modification, configuration, manipulation and storage of audio
profiles is achieved with the AT*E2EAMS (Audio Profile
Modification) and AT*E2APR (Audio Profile).
5.7.1
Audio To Mobile Station - ATMS
ATMS is the analogue audio input to the radio device.
Internally, the signal is sent to the CODEC (COder/DECoder),
where it is converted to digital audio in PCM (Pulse Code
Modulation) format. The encoded audio is sent to PCMOUT via
the internal PCM bus.
ATMS provides a DC bias when it is used as the microphone
input in Portable Handsfree applications. All other sources must
be a.c.coupled to avoid attenuation of low frequencies, and to
prevent incorrect biasing or damage to the ATMS input. Use a
capacitor greater than the value shown in the table below.
The ATMS input is a passive network followed by the transmit
part of the CODEC.
Parameter
Limit
Application driving impedance (0.3 - 3.5 kHz)
≤
300
Ω
AC coupling capacitance
≥
1
µF
Radio device input impedance (0.3 - 3.5 kHz)
> 50 k
Ω
Low frequency cut-off (- 3 dB)
300 Hz ± 50 Hz
High frequency cut-off (– 3 dB)
> 3500 Hz ± 50 Hz
Output d.c. bias level
car kit mode
0 V
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