Integrator's Manual GR47/GR48

5. SYSTEM CONNECTOR INTERFACE
29
LZT 123 7589 R1A
5.7 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 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.
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
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 kΩ
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
Additional Gain in car kit mode 28.5 dB