AL7020S, AL7024S Designer’s Guide
Doc. No. DG_7024E Altec Electronic AG Seite 21 / 32
3.8 Audio - Interface
3.8.1 Speaker-Circuit
Audio output is useful for monitoring the modem's call-progress tones and modem
system debugging, as well as for fullfeatured Voice applications. You can directly
connect a speaker of 32 to 150 Ohms to pins 63 and 64. The connection is single-
ended, with analog-ground at pin 63. Use good shielding of the audio-connections as
to avoid disturbing performance by entering RF.
The gain of the SPK output is internally adjusted and can be tuned using an AT
command. The possible range of output-levels is 4mV to 210mV rms (max. Levels).
Recommended characteristics for the speaker:
• Type: 10mW, electro-magnetic
• Impedance: 32 to 150 Ohms / 1nF (32Ohm for headsets, 150Ohms other
applications)
• Sensitivity (SPL): 100dB min
• Frequency response compatible with the GSM specifications
Table 3.8 shows the Speaker output in headset mode for different network signal
levels when the g20 is set to the maximum volume level.
Table 3.8. Headset Speaker Output at Maximum Volume Level
dBm0 mV RMS
dBm0 mV RMS
Headset
Speaker
(mV RMS)
3.14 1111.9 174
0 774.6 165
-5 435.6 132
-10 244.9 72
-15.5 130 39
-16 122.8 36
-17 109.4 32
-20 77.5 24
-25 43.6 5
-30 24.5 4
max 3000 210
Speak
