Ok, so I have several military DNVT (Digital non secure voice terminals) that I have acquired. Some of both CA-67 and TA-1042. Now the manuals (which, anyone who has ever read an Army Technical Manual will know, are not that user friendly) seem to imply that these need to hook into a switching unit before you can use them to access an outside line. Which makes sense if they are digital terminals. Does anyone know of a way to connect these directly to the plain old telephone system? Barring that, does anyone know a cheaper and easier-to-find piece of equipment than a military issue MSE switch that would allow me to use these on a normal phone line?

Thanks in advance for any help you can give me!

https://www.prc68.com/I/CA67.shtml

TA-1042

Does anyone know of a way to connect these directly to the plain old telephone system? Barring that, does anyone know a cheaper and easier-to-find piece of equipment than a military issue MSE switch that would allow me to use these on a normal phone line?

The answer to both your questions is no.

-Hal

These are 4 wire (non E&M) autovon phones. They were designed to work on the private government switching network that allowed class marked extensions to override other calls (the General, if he encountered an "all-circuits-busy", could bounce the Captain, who was on the line off the air and take the circuit.)

The Autovon is no longer with us and the simple answer, like Hal said, is No.

However, I did research for something once and the web site for the device is still up - maybe you can try them:


https://www.kvms.com/ID/39067.aspx

I did NOT use the device, but maybe their tech support can give you an answer. If it does happen to work the extra dial pad keys (Flash, Override, Immediate & Priority) will not function.

Sam

Ok, thanks for everyone's responses. I'll look further into that site.

Merry Christmas!

The link Sam gave for the two-wire to four-wire convertor looks interesting - I want to see what else that company makes. However, this has no application for your digital voice terminals. These puppies talk to an Army tactical DIGITAL switch only, using a CVSD (Continuously Variable Slope Delta) modulation scheme for the actual voice path and diphase signalling for control. One thing the TA-1042 can do, however, is work directly with another TA-1042 point-to-point, just like a pair of good old analog field phones. (As far as I know, this is the only Army digital voice terminal that can do this.) For this all you will need is a power supply of 56 VDC. A one amp rated supply should be plenty. So if you want to use the 1042, get a second one and you could have a really cool intercom setup.

Sam also mentioned the Autovon precedence keys, which the 1042 indeed does have. This raises and intersting point that I never noticed before: The 1042 and other digital sets were all made long after the original anolog Autovon system was phased out, and yet the 16-button keypad with the precedence keys seems to be the norm on all Army voice communication equipment to this day. So apparently the call priority system is still used, at least in some situations (I'm assuming, which is dangerous).

Jim
**************
Still clutching my 2500 set and refusing to let go.

Yes, I have 2 of the CA-67s, and I have them hooked up in point-to-point mode. From what I could find on the internet and reading through the manuals, the precedence keys are still functional when these terminals are hooked into an actual military communications network. They are a holdover from the autovon, but these types of phones would never work on the original autovon for the same reasons they won't work on the pots - they're all digital.

Also, the precedence keys offer some programing functionality for setting up the data processing functions of the voice terminals (this allows connections of secure voice terminals, fax machines, computers, etc).

So is a military digital switch really the only way to use these phones in any way other than point-to-point?

This is what happens when you get old and out of date.

Those are DIGITAL sets!?! With Autovon precedence keys!?! Who knew? Wow!

My experience with Autovon was on the switch side from GTE. I remember when Autovon went away and I assumed (don't you hate when you do that?) that these were the older sets. Thanks to Jim for bringing me up to date.

Sam

The precedence levels are still used on the Defense Switched Network (DSN)…which replaced Autovon. DSN

Sam, the first time I saw a TA-1042 I also figured it had to be a later generation Autovon type phone. This is a logical assumption because that is the equipment that should be appearing on the surplus market these days. What is really going on is that there is a strange "gap" in the telephone equipment being excessed by the military. They jumped from the second-to-last generation of analog phones (TA-312 2-wire field phones and SB-22 switchboards) directly to the first generation digital stuff like the TA-1024. Missing from the surplus stream is the final generation of analog equipment, like the TA-838 field phone, an Autovon-capable phone that could work on both 2- and 4-wire circuits and could be used on a POTS line. There were also all-electronic switchboards that replaced the SB-22 (can't remember the numbers) that were basically tiny portable CO switches. These and other final generation analog equipment seem to have disappeared from the face of the earth. Can any military guys on here shed some light as to why this is?


Jay, that is the million dollar question that you have been trying to get an answer to while I babble on (sorry). Yeah, we need a signal-corps veteran to educate us on this. I have also wondered if there is a commercial phone switch that uses CSVD and could be modified to work with these phones to interface with POTS. I think most of the guys who could answer this question are currently deployed overseas....

I think most of the guys who could answer this question are currently deployed overseas....

Hopefully some of them have internet connection and are as addicted to and informed by these forums as I've been the last few weeks!

Missing from the surplus stream is the final generation of analog equipment, like the TA-838 field phone....

There are some of these floating around. I've got my eye on a few auctions...I know from https://www.prc68.com/I/TA838.shtml that this unit is analog and can be used on the pots.

Again, thanks to everyone for all the feedback/help. I've gotten more responses in one day here than weeks of searching and posting elsewhere on the internet! :thumb:

Signal corps veteran here:

The DNVT needs to interface through a CVSD (continuously variable slope DELTA) card to work on a POTS (plain old telephone service). This is typically accomplished through the use of a comm modem (could also be a DLTU-digital line termination unit), which requires several other cards to function as well, including the DLPMA card (diphase loop modem ALPHA).

You are partially correct in stating that the terminal is digital and POTS is analog, but that is only one reason why it will not work. Another reason is that there is no mode of dialing from which the CO (central office) can determine who it is you are trying to reach; there is no DTMF (dual tone multi-frequency) keypad, nor is there a "pulse" function, it is only through binary conversion to DTMF that you can actually tell the phone company who to call. Yet another reason, as stated above is that the DNVT is a four-wire terminal, POTS lines are but two.

If I can help in any other way, let me know. I was very very intimate with all of these systems down to the component level in my time in the ARMY.

thanks,
Zach
[email protected]

PS email me directly, I won't get messages from this forum..

Zach -

Thanks for the info! Welcome to the Board.

Sam

Wow, I worked AUTOSEVOCOM at Corozal, Canal Zone in Panama in the mid-70's, you're really bringing back memories....thanks.