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Shared Audio Input/Output

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roys29

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I'm new to this forum and have a question. I'm trying to interface both a cell phone and GPS to my Autocom motorcycle intercom. Autocom sells a special cable for $50, but I thought I could build my own for much less. Is this a simple matter of using 1:1 small isolation transformers to couple the inputs to the output? Obviously the cell phone connection is mic and speaker but the GPS interface is uni-directional mono (speaker) only. The Autocom cell phone interface has speaker in (center of 1/8" stereo jack), mic out (tip of 1/8" stereo jack) and ground (base of 1/8" stereo jack). What can I build (passive) to share the speaker input with both the cell phone speaker and GPS audio out, and perhaps in the future a radar detector? I don't want to spend the $50-$70 for factory cables. Thanks in advance for your help.
 
The cell phone is not bidirectional, the speaker and mike are seperate devices, so 4 wires are needed. You should buy a head mount mike and earphone for the cell phone and not try to run it thru the intercom. The GPS could be put thru the intercom using a resistance pad to provide some isolation.
 
Thanks Russlk for the reply. However, the Autocom intercom is specifically designed to take a cell phone interface cable. Using a 3.5mm stereo plug, the tip is mic, center is speaker, and base is ground. Autocom sells an isolated cable ($50) that allows you to connect a cellphone and one other audio device (GPS) together so they both feed into the cell phone interface, specifically the speaker input. So my question is how can I build this isolated cable so the two speaker connections (cell phone and GPS) are isolated from each other, yet still drive the speaker connection going into the intercom?

Thanks,
 
If the intercom speaker input is high impedance, which it should be, just put 1K in series with the cell phone and GPS outputs, connected together at the phone plug. The amplifier in the intercom will make up for the 6dB loss.
 
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