I want to make my stereo switch automaticaly between inputs. If you remember way back when, I made a plug (with your help) that allows aux input to my stock '00 XE head unit. I control it with a manual switch. I want to make a circuit that allows my FRS to switch the head unit to aux automaticaly when I get a call over the radio. This way I can leave my FRS plugged in and listen to CDs and the FM radio and then have my FRS sound come over the speakers when I get a message. This would be simple enough, but I also want to be able to hear the computer input by way of a manual aux switch at the same time. So it would work like this. I have the computer and FRS plugged in to the input. I decide manually if I hear the computer or the head unit. Then if a FRS signal comes in and I have the head unit on, the aux input switches on and I hear the FRS or if I have the aux already on and am listening to the computer then when I get a FRS signal it shuts off the computer input to the head unit and allows the FRS signal through. I would want both of these options to be temporary, so that the head unit or computer sound comes back on when the FRS signal stops. Does this make sense?

It makes perfect sense. Your description is far better than the specs I get at work. I have to think on this a while...

Yeah, I rewrote it about three times and finally gave up because I knew it would be confusing no matter how I wrote it. It all seems pretty simple and straight forward in my head though.

Sort of like a priority vox switcher. I started drawing up a switch box that could do something like what you describe last year. My wife and I were getting tired of
1) Stepping on each other when we both tried to key our FRS units.
2) tired of listening the to cacophony of the CB and FRS and scanner units.
So I drew up a switch box that would route the two FRS mics to one frs unit and interlock them so that once one of us keyed the other couldn't, with an option for "Pilot over Co-pilot" priority.
And the monitor took the CB and FRS and Scanner outputs and gave priority in that order.
I prototyped one part of the circuit using some optical relays and stole the priority circuits off the web (just basic vox circuits.). You are more than welcome to them if you think they might be of any use to you. Since I never built the complete thing I have no idea what the end product would be like.

Go ahead and post them. I'd like to see what it looks like.

I'll drop them in email tomorrow as they are on my work workstation. I've nowhere to post them online. They are in Xcircuit format so I'll probably have to mail you the postscript .ps files. It might be worth running them by ElectroKen (he probably could use a good laugh!) to see if they will actually do what I think they will do.

Edit: Mail sent.

Xterrian, Did my mail get through to you?

Yeah, thanks. I just got back on my server tonight, so I haven't looked at them yet.

I'd be happy to take a look at them. There is usually no need to reinvent the wheel.

ElectroKen, I'll send them as long as you promise not to laugh!
Can you take .ps (postscript) files? My circuits are drawn with Xcircuit (unix and free).

Xterrian, I replied to your email. Short story:
check out this site for a ps viewer. You will need two downloads, Ghostscript and gsview for windows.

Hey Xterrain, how's your carputer project coming? I've got all the parts for mine, now I just have to do some surgery on the case, run the wires to the battery, put it all together, and fire it up. Looks like it's going to fit under the seat, which is good. Trying to remember to take pics of each step along the way. It's definitely a major undertaking.

Mine is all apart on the dining room table. I added a T.V. card and it's too tall to fit under the seat anymore. The T.V. card is one of the half height ones and was still too tall. I'm building a new center console that will hold it all. I have computer parts all over the table and styrofoam blocks stacked everywhere. The wife hasn't said a word, but her parents will be here soon and I notice that she is working really hard to hold it in.

Yeah, I can handle the postscript files.
And I promise I won't laugh. I've seen many schematics drawn on bar napkins.

I don't think we'll hear much from Xterrian for a while. His wife is going to kick his ass soon.

My wife is too sweet for that. When I got my first body damage in Odessa Canyon she was supportive and nice about it. I bought her diamonds for Christmas tonight, so she should be OK. She may get a little PO'd when she finds out how much I spent, but it was $9 less than my winch and I think she's worth it.

Xterrian, you better tell her they were $9 more not less than what you spent on your truck.

ElectroKen, I'll need your email address (by PM) unless Xterrian has already passed them along.

You have a valid point about that $9. I never even thought about it. I don't have Ken's address either. You know how those celebrities are about their privacy.

Not to hijack your thread, but what are you using for a display in your truck? I've got a completely new setup going, but my display isn't wanting to play nice. I'm thinking about trying to locate a 12" display - got a 10.4 right now.

Shameless bump. What do you think Ken?

I finally got around to installing Ghostscript and GSView on this machine. I'm just seeing the schematics that Kayak_X sent me for the first time. I have to figure out some of the part numbers. The dual optically isolating switches and the voltage monitor are new numbers to me.

The circuit that kayak_x sent me looks pretty darn good and would be a great starting point for the audio switcher. The only change that jumps out at me is the need to knock down the gain of the vox circuit to handle the much higher line levels in the audio system. Change the 100k resistor to about 10k and you'll be in the ballpark.

ElectroKen, Thanks for looking at them! I'll have to build them myself now that you think they might even work!
Xterrian, I sent you a refreshed drawing with Ken's suggested change.

I guess I'll be hitting the radio shack website to order the parts. If Electroken says it'll work I believe it.

It looks good on paper. Lots of things look good on paper.

I don't think you'll find too many of those parts at Radio Shack. It looks to me like kayak_x shops at DigiKey.

Will I have to program the ICs?

Nope. Nothing to program.

Either of you want to build one for me? Maybe you could build two Kayak, and I could buy one. I only need two inputs. FRS and Computer, so the second priority switch would be unecessary. I also need it to switch a 12v+ power source to switch the head unit to AUX. I'm suddenly worried I would screw it up.

Looking at the priority switch circuit again, would it be possible to use both sides of the 7141-2B instead of using the second 7141-2A?

One's normally open, the other is normally closed, so I don't see how you could get away with using both parts of either one. There is a single circuit version of each but experience has taught me that they aren't much cheaper and you usually fry one.

I'm not sure when if ever I'll get around to building my version, maybe this spring, but if you haven't built yours by then I would be happy to cobble something up for you.

How about a parts list with sources? I'll get to work on it and build one for you.

Thanks for the offer but I'll probably tinker around a bit more before I build my prototype.
I found a Ramsey "mini-kit" at fry's for building a simple vox circuit that I'm going to muck around with to see if it will serve.
BTW: The parts can all be had from www.digikey.com.
There is nothing special on the parts list other than the op-amps and the opto-relays and the part numbers came from the digikey catalog.