EG_GenPro78e_1003_UG_007_UK
Page 31 / 41
Description and non-contractual illustrations in this document are given as an indication only.
ERCO & GENER reserves the right to make any modifications.
7.4 Audio
The audio interface is a standard interface for connecting a telephone handset (the command AT$VSELECT
enables you to select the handset, please refer to ERCO & GENER "Commands List").
Echo cancellation (see command
AT$MICAEC
) and noise reduction features are also available to improve
the audio quality in hands-free applications.
ERCO & GENER recommend the use of the following cable: DATA/AUDIO Sub D 9pts Fem / Sub HD 15pts
Male / RJ9 (order code 4404000205) and a telephone handset (order code 3153400000).
Table: Pin identification
Pin name
SUBD 9 F pin number
SUBD 15 M-HD pin number
DCD/Buzzer 1
1
RXD 2
6
TXD 3
2
DTR 4
8
GND 5
9
DSR 6
7
RTS 7
12
CTS 8
11
RI/3.8V 9
13
RJ9 pin number
Micro +
1
4
S
2
10
Speaker -
3
15
Micro -
4
5
7.4.1 Microphone
Differential microphone inputs are used to help reduce common–mode and TDMA noise. They are ESD
protected.
An electret type microphone (0.5 mA / 2 Volts) may be connected directly to these inputs allowing the
connexion of a telephone handset.
The microphone impedance is approximately 36 k
Ω
.
The gain of the microphone input may be internally adjusted by a differential amplifier and may be defined by
using the command
AT+PREAMP
(see the ERCO & GENER “Commands List”).
The amplifier has a gain of 25.6 dB and a Bias generator providing an external voltage of 2 or 2.5V for the
Bias microphone.
Table: Pins description
Signal name
Pin number Sub HD
Connector
I/O
Type
Description
CMIC2P 4 I
Analogue
Microphone
+ve
CMIC2N 5 I
Analogue
Microphone
-ve
