some clarifications

the onStar system i think is only available in the US. On this document i refer to the onStar interface, but i think the right name to call it is the telephone interface.

The system i'm developing is in fact to use the saab telephone interface to feed the signal. Starting today i will call it telephone interface.

here is what i have to far:

* the saab telephone interface is only monophonic. To feed a stereo signal some modifications have to be done to the radio. check previous postings for this.

* to activate the telephone interface the TEL-MUTE pin has to be connected to ground.

* the electronics i'm developing are to be able to use the iPod, or in fact any audio device, with the telephone interface. The circuit is required to let the actual telephone to override the output in case it becomes active.

* the system will be controlled by a switch with 3 positions: off, iPod charge and charge plus audio from the iPod.

* an additional input (1/8 stereo plug) is available to connect other device like an satellite radio. If something is connected to this plug the iPod will be disabled and the external device will feed the radio.

* to simplify the wiring to the iPod and to have a variable gain amplifier to be able to match the signal level from the iPod, telephone interface and external signal to the radio a belkin car adaptor is used as part of the circuit. Searching for the links for this page i just noticed that belkin has the same car adaptor in black! The black one will go much better with my car interior. By now i will settle with the white one.

* to physically mount the iPod to the car i will use a combination (work in progress) of the saab phone bracket and the belkin iPod holder. The electronics will go inside the saab phone bracket.