Author Topic: North Signal Corps Deal  (Read 874 times)

Offline LarryInMichigan

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North Signal Corps Deal
« on: September 20, 2011, 01:06:09 PM »
A North Signal Corps phone just appeared on ebay (http://www.ebay.com/itm/U-S-ARMY-SIGNAL-CORPS-ROTARY-DIAL-TELEPHONE-MODEL-TP-6-A-WORKS-/250896411481) for a BIN of $17.50.  If you have been looking for one of these, now is your chance.  At that price, it will go quickly.

Larry

Offline ESalter

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Re: North Signal Corps Deal
« Reply #1 on: September 20, 2011, 01:53:17 PM »
Thanks for the heads-up!  I offered $15 and it was automatically accepted.  When it shows up I'll post some better pictures.  They say it works, so it should make a great addition to one of our displays.  ---Eric

Offline LarryInMichigan

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Re: North Signal Corps Deal
« Reply #2 on: September 20, 2011, 02:06:46 PM »
$15 sounds like a great deal.  There isn't much to go wrong on one of those.  The handset cord looks like it might need to be shortened a bit, and it obviously needs an AE dial card retainer.

I bought one in March for $16.50 (http://www.classicrotaryphones.com/forum/index.php?topic=4513.0).  It works perfectly, and it's interesting to compare it to a North Galion, which is completely different inside.

Larry

Offline ESalter

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Re: North Signal Corps Deal
« Reply #3 on: September 28, 2011, 08:31:34 PM »
Here are a couple pictures of the inside of the phone.  I was surprised at the markings on the bottom of the dial.  It's cleaning up rather nice, should have it done in a day or two.  ---Eric

Offline GG

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Re: North Signal Corps Deal
« Reply #4 on: September 29, 2011, 01:15:21 AM »


What I've always wanted to know is: what purpose is served by those extra off-normal contacts on the dial?  Something to open the transmitter circuit even as the receiver and the rest of the transmission network are shunted?  And if so, was that intended as an ad-hoc security measure by which someone could rotate the dial partway and stick a pencil in it, so as to cut off any "hookswitch bypass" bugging attempts?  Or was there some other purposes served by this, for example for use in 4-wire line circuits, or something else?   

(Hookswitch bypass involves wiring resistors of > 10K across the hookswitch whereby to enable a trickle of current through the phone, sufficient to activate the carbon mic without tripping the linefinder at the CO.  Then the eavesdropper would connect an amplifier across the line anywhere between the phone and the CO, and be able to overhear room conversations conducted near the phone.  Anyone armed with a basic photo of the interior of the phone could detect one of these unless it was very cleverly hidden, and anyone with a basic knowledge of telephone sets could find one even if it was cleverly hidden.)