atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1A2 400D vs 400E Question

I've been installing 1A2 systems for many years. Only recently have I been playing around with dial tone that's not from the ILEC. As discussed here, I've discovered that 400D line cards won't work (ring) with a VOIP ATA or with local dial tone from a switch such as a Panasonic. I do have a few 400E cards in my junk box and those do work fine. Is there a way to modify 400D's to work?? Does anyone know what the difference in the design of the 400D and 400E cards is?? Thanks Bob

See this earlier post on the subject for the answer to your question:

https://www.sundance-communications.com/cgi-bin/ultimatebb.cgi?/ubb/get_topic/f/35/t/000229.html

Sam

The 1400E had a couple of features not found in the
in the 1400D.

Provided a LED on the front of the card showing the status of the line it is serving.

Used also for MOH feature. I think (46 years ago ).

Thanks for the help and suggestions. Is there any way to 'fake' out a 400D to work like an 'E'? I've got tons of 'D's by only a few 'E's.

Not that I'm aware of. I reviewed the schematics and found that this really isn't a shortcoming of the card. These were designed to work with traditional central office switches where the tip is grounded. Today's IADs, channel banks, etc. don't provide this because they have no reference to ground (AKA: "floating"). I'd imagine that some of these devices have options to emulate a "real" central office switch, but there are so many of them out there.

If it was a simple trick, WECO would have just come out with a revision of the 400D instead of jumping to an entirely new design with the 400G.

Same thing with ITT, going from D to E. It was probably too much of a change in circuit design to be addressable through just a modification.

Thanks Ed - That the 400D's can't be modified doesn't supprise me, but I thought I'd ask. Funny thing is I had not connected my Panasonic 824 to the 1A2 in a while. When I did, the KTU does ring from the 824 with the 400D. The VOIP ATA however, will only ring with the 400E. This wasn't an exhaustive test, but I did try 5 or 6 'D's and they all worked with the 824, none with the ATA.

Many collectors of old telephone and key systems use a Panasonic key system as a "tandem" to provide ringing current that will activate legacy equipment. Some Panasonic KSU's will pass CID, too. They are available cheap on Ebay and other sources.