you can usually make mods to make it work with out the common ground, but 
you're right, he'll  need a switched jack.
----- Original Message ----- 
From: "Butch Bussen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Sunday, July 19, 2009 6:22 PM
Subject: Re: Wiring Earphone Jack


>I forget what they're called, but you'll need a switched jack, actually
> it would have 5 terminals.  Ground and left and right hot which is what
> would contact the left and right on the headphone plug.  Fourth and
> fifth terminals go to each speaker and are connected when the plug is
> removed.  This would only work if the speakers share a common ground
> which isn'
> t always true particularly with output ics used these days.
> 73
> Butch Bussen
> wa0vjr
> open Node 3148
> Las Vegas
>
>
> On Sun, 19
> Jul 2009, Mark wrote:
>
>> Hi
>>     I am trying to wire an earphone jack in to a stereo that has only =
>> built in speakers. I bought a "stereo Jack" from radio shack. The =
>> trouble is there are only three contacts on the jack. I am guessing =
>> left, right, and ground. How do I get the audio to switch back to the =
>> speakers when the earphone plug is removed from the jack?
>>     Any help is appreciated.
>>
>> God bless,
>> Mark
>> --=20
>>      Currently in Pendleton, Eastern Oregon Regional At Pendleton, =
>> Oregon Clear, 84.0=B0F Wind:WSW-250=B0 at 9mph
>>      Stewardesses is the longest word that is typed with only the left =
>> hand.
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>>    =20
>>
>>