RTCU MX2 turbo Technical Manual V2.04
Logic IO ApS.
Ph: (+45) 7625 0210
Holmboes Allé 14
Fax: (+45) 7625 0211
8700 Horsens
Page 18 of 36
Email: [email protected]
Denmark
www.logicio.com
Hands-free connector
The RTCU unit has a 4-pole 2.5mm jack connector for connecting a hands-free set to the built-in
GSM modem. The speaker output is amplified through the internal Class-D amplifier and is a
differential (balanced) signal. A loud
speaker of 4/8 Ω can be connected
directly to the speaker
output. The microphone input is differential in order to minimize GSM (TDMA) noise. An audio
line transformer must be used to convert the signal to a single ended signal, when connected to
external equipment that does not have a differential (balanced) input. Otherwise the GSM noise
will not be suppressed / cancelled and will pass through all the way to the loudspeaker.
The microphone signal is biased internal for active microphones.
4 pin headset connector overview
Pin
Name
Description
1
Mic +
Microphone positive Input
2
SPK +
Speaker positive output
3
Mic -
Microphone negative input
4
SPK -
Speaker negative output
Microphone characteristics
Parameter
Min.
Typ.
Max.
Unit
Working voltage
1.65
1.8
1.95
V
Working current
20
1000
µA
Speaker characteristics
Parameter
Min.
Typ.
Max.
Unit
Working voltage
3.5
3.8
4.2
V
Output power (THD+N=10%)
0.83
2.05
W
Please consult the RTCU IDE documentation for more information on using the Hands- free
interface.
External voice output
A voice audio output is available on X2 connector. Digitized audio can be played through this
output by the application interface. Please consult the RTCU IDE documentation for more
information about enabling the xVoice output and playing digitized voice messages.
The output is at line-out level (3Vpeak-peak), and internally shared with GSM voice line.
