DIY Plantronics headset adapter for iPhone 3 GS
Sorry for waking up an old thread: I made an adapter from a 3,5mm 4-pole connector and used 2 resistors at 120 ohm as a basic summary circuit.
It connects a Plantronics headset to my iPhone 3GS. It works, and sound quality in telephone calls is good, but I would not use it to listen to music
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There is a button on the headset cord, which short-circuits Plug tip (microphone) to ground (sleeve). That button does not have any function when connected to the iPhone.
The summary circuit might not be needed, but I added it for safety (don't want to damage the iPhone). At least it does no harm. Resistance value can be between 47 -> 200 ohm I believe, take what you have. Select 0,1w resistors if you can to save space.
Apple iPhone pinout can be found here:
http://pinouts.ru/PortableDevices/iphone_headphone_pinout.shtml
My Plantronics (mono) headset pinout is:
Plug tip: Microphone (white)
Middle: Ear-piece (+) (red)
Sleeve: Ground for both microphone (copper) and ear-piece (blue)
Strip the headset chord
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Cut the 2,5mm stereo plug from the headset. Strip the outer sleeve.
Red and blue cords are coated with a thin resin film that is best removed by burning them with a cigarette lighter. Be careful, the resin burns fast. Neglecting to burn off the resin will result in poor soldering properties.
Strip the white cord from its plastic sleeve. Join all strands of the plain copper cord. Be thorough, one single strand in the wrong place can ruin (i.e. short-circuit) the whole adapter.
Connections:
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Left and right channels from the iPhone are each connected to a 120 ohm resistor. The other end of the resistors is shorted and soldered to the red cord (Ear-piece+ on the headset).
Microphone on iPhone ->White cord (Microphone on headset)
Common/ground on iPhone->Blue and Copper cords (ground on headset)
Snug fit
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I managed to cram the summary circuit and all soldering joints into a standard 3,5 mm plug case. Some care is needed, but it fits right in there if you select low-wattage resistors.
The microphone on my headset is not very sensitive but it works although you have to speak up a bit. Newer headsets with more sensitive microphone might behave better.
Hope someone can make Some use of this
