Paging with McGohen Amplfier

Answered Question
Nov 21st, 2007

Customer has an old amp (McGohen MS-s1004) which connects today to an external transformers RCA connection on one end, and hard wired via analog pair to legacy PBX on the other end for paging purposes.

So the question is can I run copper pair from FXS on router and hardwire it into old transformer and get paging working?

Correct Answer by Maulik Shah about 9 years 3 months ago

typically older paging systems use E&M ports:

If you want to use an FXS port - you will need another entity such as a Bogen TAMB to terminate signaling

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Overall Rating: 5 (2 ratings)
SBCdd7343 Thu, 11/22/2007 - 05:38


Thanks for the quick response.

Do you recommend we just purchase an E&M vic? Or purchase a TAMB and use and FXS port?

In our scenario, the customer has a very old McGohen amplifier. The amp connects into an RCA connector on an external transformer. The external transformer also has screws where you can wire it to a telephone device (two wire). Do you know what two pins should be used from the transformer side going to the E&M interface on the router?

Rob Huffman Thu, 11/22/2007 - 06:49

Hi Jerry,

This should be a challenge for sure :) I would try to trace the wiring back to the Legacy system or at least disconnect the wires (at the Amp) and put a "butt set" across the leads to see if there is dialtone or not.

If there is dialtone then you can probably just use a FXS Port in a similar config. The two pins on the external transformer are probably just to hardwire the power if you chose not to use the RCA Plug, so any connections you do will be at the Amp most likely.

From what I have just read, they stopped building these Amps in the 50's so it may also be time for an upgrade for this customer to go along with the work you must be doing.

Here is the only type of tech info I could find;

" It provides discrete paging in up to 4 sep zones or simultaneous all call. It will accept voice page from either a microphone or any 600 OHM balanced telco output. It has a built-in switchable pre-page tone alert as well. Source input (music) & outputs are std RCA terminals for easy hook-up to ea zone amp"

Just some thoughts!


PS: I did find an answer for your request for SRST Licensing info.

SBCdd7343 Thu, 11/22/2007 - 12:12

HI Rob,

Thanks for the detailed response. You are always so helpfull.

I'm a bit nervous on this one as if we commit to allowing existing amp setup, we HAVE TO get it working (which I don't feel like I can guarantee). On the other hand if we don't commit to this setup, we will probably loose the deal.

In regards to the setup. If we connected directly into the amp, how would we do that. I wasn't aware their was interface that would accept copper wiring from a phone system. Could you descripte the mechanics of how this would work? I know you are a veteran from the Telco world, so hoping you can describe very granular how the signaling would work from a router to the amp.

P.S. Thanks also for the quick response on teh SRST licensing. much apprecaited.


Rob Huffman Thu, 11/22/2007 - 13:02

Hi Jerry,

You are most welcome my friend. Is veteran just a nice way of saying "old" :) Just kidding!

In many/most cases there is some sort of interface mechanism between the Paging System and the phone system like the TAMB that Maulik so nicely noted. Without seeing this setup we can only speculate as to the exact configuration, but it is likely one of the two noted so far. Here is my rather lame overview of the two;

E&M - Won't have any dialtone when testing across the Pairs from the Legacy system. Will have an access code/codes (usually far different from the working dialplan ex: 2 digit access code vs 4 digit dialplan) then when called from a user phone will activate a set of contacts on the E&M Card and allows the Page to go out over Tip and Ring (Pins 4&5) to the Paging Amp from the previous Cisco doc from Maulik. The Transformer that you spoke of is likely only for some sort of Aux power for the Amp.

Dial Access - will have dialtone when testing across the Pairs from the Legacy system. Will have an access code/codes (usually similar to the working dialplan ex: 4 digit access code vs 4 digit dialplan) This dial Access will have to go through a mechanical relay that is either standalone or built-in that is tripped when the user rings up the circuit. The set of contacts will complete the "speech path" from user phone to the Paging system.

I'm not sure the about scope of this deal size wise, but to guarantee anything with a fifty year part sounds sketchy at best. If the deal is a good one, and the user is adamant, a new Paging System is not usually a huge expense.

Hope this helps!



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