Telecom Technical Need info on E&M signaling

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Subject Author Date
Need info on E&M signaling sandeep 10-15-06
Posted by sandeep on October 15, 2006, 9:43 am
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Hello All,

I have some basic knowledge about E&M, and have practically used it.
But concept wise, I am not very clear... So i am posting a few queries
related to E&M to get a better picture.

1. Normally I have used E&M in a back-toback configuration. i.e. I have
an E&M interface set to say type 4, and another interface also set to
type 4. Both of these are on the same VoIP gateway. And hence no PBX
coming into picture here. Thus, I guess I am using two signaling units,
rather than a signaling unit and a trunk unit ( Hope I am right here
!!!!). I connect the two using a cross E&M cable ( i.e. E<-->M, M<-->E,
.........). My query is that will the cross cable be still used if,
instead of the other interface on the VoIP gateway, I connect it to a
PBX. Or will it HAVE to be a straight cable.

2. With using the circuit diagramof Type II, i tried to visualise the
back to back configuration. What diagram I obtained was as follows:

___________________________________
Signaling Unit 1<------------> Signaling Unit 2
___________________________________

E ( open)------------------------M ( GND)
|
SG--------------------------------SB ( -48V)
___________________________________

M ( GND)------------------------E ( open)
|
SB ( -48V)-----------------------SG

My Question is if either side has to indicate Offhook, then it will
always be that E Lead has to be asserted. Have I understood it right.
Whereas the basic working principle of E&M ( be it E&M Wink or
immediate) states that once the side that is initiating the call
asserts the M Lead, and then dials the digits, the Recieving end will
assert the E Lead to indicate the call is connected. So i am not able
to correlate this principle with the figure shown above.


Thanks in advance,
Regards
Sandeep


Posted by Ron Kritzman on October 15, 2006, 3:29 pm
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sandeep wrote:
> Hello All,
>
> I have some basic knowledge about E&M, and have practically used it.
> But concept wise, I am not very clear... So i am posting a few queries
> related to E&M to get a better picture.

Just remember that E and M stand for recEive and transMit.
The M lead does something and the E lead listens for something to happen.



--
Emoveray ethay Igpay Atinlay otay eplyray


Posted by obsidian on October 15, 2006, 6:40 pm
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hmm, I learned E for Ear and M for Mouth as a way to remember

--
obsidian


> sandeep wrote:
>> Hello All,
>>
>> I have some basic knowledge about E&M, and have practically used it.
>> But concept wise, I am not very clear... So i am posting a few queries
>> related to E&M to get a better picture.
>
> Just remember that E and M stand for recEive and transMit.
> The M lead does something and the E lead listens for something to happen.
>
>
>
> --
> Emoveray ethay Igpay Atinlay otay eplyray
>



Posted by Dana on October 15, 2006, 6:49 pm
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> hmm, I learned E for Ear and M for Mouth as a way to remember

Ear = Receive, Mouth = Transmit
>
> --
> obsidian
>
>
> > sandeep wrote:
> >> Hello All,
> >>
> >> I have some basic knowledge about E&M, and have practically used it.
> >> But concept wise, I am not very clear... So i am posting a few queries
> >> related to E&M to get a better picture.
> >
> > Just remember that E and M stand for recEive and transMit.
> > The M lead does something and the E lead listens for something to
happen.
> >
> >
> >
> > --
> > Emoveray ethay Igpay Atinlay otay eplyray
> >
>
>



Posted by sandeep on October 16, 2006, 6:58 am
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Dana wrote:
> > hmm, I learned E for Ear and M for Mouth as a way to remember
>
> Ear = Receive, Mouth = Transmit
> >
> > --
> > obsidian
> >
> >
> > > sandeep wrote:
> > >> Hello All,
> > >>
> > >> I have some basic knowledge about E&M, and have practically used it.
> > >> But concept wise, I am not very clear... So i am posting a few queries
> > >> related to E&M to get a better picture.
> > >
> > > Just remember that E and M stand for recEive and transMit.
> > > The M lead does something and the E lead listens for something to
> happen.
> > >
> > >
> > >
> > > --
> > > Emoveray ethay Igpay Atinlay otay eplyray
> > >
> >
> >

I am aware that E receives and M transmits. But how will u guys explain
the circuit with respect to type II. I have shown the type II connected
in a back-to-back configuration, and hence uses cross cable to connect
two signaling units.

And do you guys mean that always the M lead on one end will be
connected to the E lead on the other and Vice versa.

Could you guys refer some sites where they have good documentation on
the different type of E&M and the different E&M signaling protocols. I
searched thru google, but found info where M lead on one end will be
connected to M lead on the other end. With this I came up with a
circuit diagram as above.

Thanks in advance,
Regards
Sandeep


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