Table of Contents
Advertisement
5.7 Analogue Audio
5.7.1 Audio To Mobile Station - ATMS
LZT 123 7589 R1A
5. SYSTEM CONNECTOR INTERFACE
Pin
Signal
57
AFMS
59
ATMS
60
AGND
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).
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 Hands-free 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
Application driving impedance (0.3 - 3.5 kHz)
AC coupling capacitance
Radio device input impedance (0.3 - 3.5 kHz)
Low frequency cut-off (- 3 dB)
High frequency cut-off (– 3 dB)
Output d.c. bias level
Additional Gain in car kit mode
Dir
Description
O
Audio from mobile station
I
Audio to mobile station
-
Ground (return) for analogue audio
car kit mode
Limit
300
1 µF
> 50 k
300 Hz ± 50 Hz
> 3500 Hz ± 50 Hz
0 V
28.5 dB
29
Advertisement
Table of Contents
