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 Post subject: Signal Corps Plugs Question
PostPosted: Jun Tue 26, 2012 6:19 pm 
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Joined: Jun Tue 26, 2012 5:49 pm
Posts: 5
Location: Tucson, Ariz.
Hi all,

new member here and I'm learning as I go! I'm trying to understand the different plugs, jacks, etc. for 1940s military radio equipment.

Question(s):

1) What is the difference between the plugs, e.g. PL-54, PL-55, and PL-68? Is it in how they are physically constructed and if so what is the difference?

2) The difference between a PL-54 and PL-354 had to do with the receivers R-14 and ANB-H-1 and Ohms, but then they are connected to receivers/interphones using an extension with a jack JK-26 and a PL-55. What does the PL-55 do?

Apologies if this sounds confusing - it is because I'm confused!

Thanks, Jeff


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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jun Tue 26, 2012 8:26 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 30698
Location: Pocasset, Cape Cod, MA
Welcome to the forum.

The PL-55 is a normal 1/4" phone plug. The PL-54 is a shorter one, only used with an in-line jack as an extension. The PL-68 is a 3-contact mike jack, smaller diameter, won't fit a 1/4" jack.


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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jun Tue 26, 2012 8:43 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3083
Location: Seattle WA US
Here's a try for your first question:
PL-55 and PL-47 are both "standard" two conductor, 0.250 inch diameter phone plugs. Also known as PJ-055B. They mate with military JK-24 and JK-34A jacks or any quarter-inch two-conductor phone jack such as Switchcraft C-11.

PL-68 is a 3-conductor, 0.206 diameter phone plug. Also known as PJ-068. They mate with military type JK-33 jacks or Switchcraft C-12B. Similar plugs and mating jacks were used in Western Electric telephone switchboards as WE plug 109. There is also a Switchcraft S-13B jack which apparently mates with both Signal Corps PL-68 and WE-109. There may be subtle differences between Army PL-68 and Signal Corps PL-68 ???? I believe these were used for carbon microphones with the third lead for the PTT switch during WWII.

PL-54 is a short, quarter-inch diameter phone plug which mates only with JK-26 inline jack. I believe these were used during WW-II for quick disconnect of flight helmet-mounted headphones.

Sorry, but I don't understand your second question.

--Chuck


Last edited by K7MCG on Nov Wed 20, 2013 10:20 pm, edited 1 time in total.

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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jun Tue 26, 2012 11:09 pm 
New Member

Joined: Jun Tue 26, 2012 5:49 pm
Posts: 5
Location: Tucson, Ariz.
Hi and thanks for the info - helped clarify things for me.

Ref. Chuck - the second question was answered through the first - essentially I was wondering why you needed a different plug to connect to the receiver/interphone/etc. - apparently as the saying goes - it was a size issue.

Just ordered a PL-354, JK-26, and JK-34 to complete my small set-up.

Thanks again, Jeff


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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jun Wed 27, 2012 2:11 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 3520
Location: Monterey California USA
PL54 looks like a PL55 but it is considerably shorter, and the only application I have ever seen them used on is the bail-out disconnect junction at the end of the short cord on the aircraft headphone assemblies. When I was a kid I found a tub of PL-54's in a surplus store for 10 cents each and thought I had it made until I brought some home and found they were far too short to do anything when plugged into my radio headphone jacks. :(

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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jul Tue 03, 2012 12:09 pm 
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Joined: May Tue 16, 2006 12:54 pm
Posts: 163
Location: Gordonsville, Virginia
It is certainly a confusing mishmash of numbers for what ostensibly seems like would be a simple subject. If you add in the US Navy variations, it gets even more messy.
I tried to do a sorting process on them at the bottom of http://aafradio.org/flightdeck/Peripher ... dsets.html but I don't pretend that it is a complete answer. Look for this photo and its caption:
Image

73,

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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jul Tue 03, 2012 10:45 pm 
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Joined: Nov Sat 27, 2010 6:15 pm
Posts: 5449
There were also 3 conductor variations. I no longer have any.


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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Jul Tue 03, 2012 11:33 pm 
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Joined: May Tue 16, 2006 12:54 pm
Posts: 163
Location: Gordonsville, Virginia
Absolutely. I need to add the microphone connectors in a future update, I suppose. There were several variations of those, but the configuration diverged with the small two pin break-away connectors used in the last half of the war, intended primarily for oxygen mask applications. Since few hams (even dedicated military radio buffs) use an oxygen mask microphone, I decided to ignore those.

Hey, I had to stop somewhere... :?

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http://aafradio.org


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 Post subject: Re: Signal Corps Plugs Question
PostPosted: Nov Wed 20, 2013 6:16 pm 
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Joined: Nov Wed 20, 2013 6:14 pm
Posts: 1
Im really sorry to bring back this dead post. But I recently acquired a Shure Military Mic with a PL-68 plug on it.
Is there any known converters out there that would allow me to use this on a computers 8mm jack?

Thanks
Jesse


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