sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems General thanks and Exbar security linecard question

So what I know from what I have read in various bits and pieces is that the purpose was indeed to remove the tip and ring connection from the sets once they were on hook. This seems to be reinforced by the fact that with this card in the system once you put the set on hook a short time after the the hook closes you can hear the relays on the card click which I assume is the T&R being lifted. I don't think they were meant to work with an exclusion key but I could be wrong there.

The theory being that if a set was on hook but a line key was selected that you could supposedly "listen" on the sets... Now how this would have been done seems obscure to me but I suppose with enough initiative you could intercept the lines anywhere from the CO to the equipment closet. Now I think we all assume this to be ridiculous but obviously some people took the threat seriously enough to make these cards in the first place...

I suppose the same thing could be a concern on VOIP lines. I have the discontinued TMobile "@home" VOIP lines for my work and home land lines. They are provided by a SIM card based Cisco router that presents 2 regular POTS lines. They actually work fine with the 400D cards and even work most of the time with the 565 dial sets (which surprises me). Along the same lines of cold war security it still makes me wonder who could have access to Mics and receivers in your phones via the VOIP router. Not that I think I need a tinfoil hat but still...

I do think there might be other interesting options on the cards and that is why I was looking for documentation. I guess the easiest thing is to get one in and have the lines connected and play with the switches and see what they do...

Anyway guys I appreciate the ideas. I'm just a bit happy I could stump the experts a little bit right off the bat

"Along the same lines of cold war security it still makes me wonder who could have access to Mics and receivers in your phones via the VOIP router. Not that I think I need a tinfoil hat but still.."

Actually given access to your network with a $29 hub, laptop with Wireshark I can play back both sides of your SIP based conversation. Off of your LAN only a little more difficult.

You are right about the exclusion key being manual and thus subject to human error, The Exbar cards took the human intervention out (if they are optioned correctly). The military is very serious about voice security. I have installed optical isolators, mercury switch handsets, push to talk handsets, STEs and STUs, and noise generators on windows in the effort to disrupt eavesdropping.

There was even a software patch several years ago for Cisco that prevented the on hook speakerphone mic from being use as a hot transmitter.

Tin foil hat time:

RE how could a spy possibly listen in via an on-hook phone? One of the things the three-letter agencies worried about was ringers bridged across the line, mainly C-type ringers with big wire-wound coils. Someone, somewhere came up with the theory that this ringer coil could be used as a listening device. I don't know it it was ever proven or actually demonstrated, but they did go to great lengths to prevent it. Disconnecting T&R was one way, especially for single-line phones with bridged ringers.

Crazy, I know. But I have actual government manuals around somewhere that discuss it in great detail.

Jim
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Speaking from a secure undisclosed location.

Now that's an interesting slant, I didn't even think of that possibility. Seems you would need a tremendous amount of gain to pick up sound on a ringer coil...

I actually have a very odd thing I have never seen before: A 565 HD set that has a dial blankout plate. The number card has a 202 number on it and keys 1 and 2 had 4 digit numbers. When I Googled the number it came back as a Department of Defense number.

I guess the other aspect of all this security is to not let someone dial out. I dont think I have ever seen a 1A2 set with out a dial or touchpad...

Commonly used in Command Post, towers, and alternate HQs for ringing hotlines. The button would flash upon ring, pickup the handset and answer the emergency...never used for outbound calling. Eliminating the dial pad prevented the set from being tied up on non official business.

Here is an old post about these cards from this forum. Arthur gave a good explanation on them:

https://sundance-communications.com...305/Exbar_security_line_cards#Post488305