Looking for E&M (earth & magnet) signalling specification

[frigidzephyr]

I have searched google and various forums such as tek-tips, but cannot find a spec sheet or data sheet on E&M.

I can find many product data sheets that make reference to the signalling protocol but not a full description of it.

Anyone know where I might find this? I don't know a whole lot about E&M in general.

I want to learn about Analog E&M and Digital E&M.

Thanks in advance guys.

 

[Dexman]

I think E&M stands for "Ear and Mouth"

If it ain't broke, I haven't fixed it yet.

 

[Deweyhumbolt]

Check in a book called, "Newton's Telecom Dictionary" under E&M Signaling. Yes, Ear & Mouth.

Adversity is Opportunity

 

[Bas1234]

Found some thing here for you.

http://www.cisco.com/en/US/tech/tk1077/technologies_tech_note09186a0080093f60.shtml#wiring

E&M Interface Types and Wiring Arrangement
There are five different E&M interface types or models named Type I, II, III, IV, and V (Type IV is not supported on Cisco platforms). Each type has a different wiring arrangement, hence a different approach to transmit E&M supervision signaling (on-hook / off-hook signaling). The signaling side sends its on-hook/off-hook signal over the E-lead. The trunking side sends the on-hook/off-hook over the M-lead.

For more information and pinout diagrams of E&M types, refer to Understanding and Troubleshooting Analog E&M Interface Types and Wiring Arrangements.

E&M Type I—This is the most common interface in North America.

Type I uses two leads for supervisor signaling: E, and M.

During inactivity, the E-lead is open and the M-lead is connected to the ground.

The PBX (that acts as trunk circuit side) connects the M-lead to the battery in order to indicate the off-hook condition.

The Cisco router/gateway (signaling unit) connects the E-lead to the ground in order to indicate the off-hook condition.

E&M Type II—Two signaling nodes can be connected back-to-back.

Type II uses four leads for supervision signaling: E, M, SB, and SG.

During inactivity both the E-lead and M-lead are open.

The PBX (that acts as trunk circuit side) connects the M-lead to the signal battery (SB) lead connected to the battery of the signaling side in order to indicate the off-hook condition.

The Cisco router / gateway (signaling unit) connects the E-lead to the signal ground (SG) lead connected to the ground of the trunk circuit side in order to indicate the off-hook condition.

E&M Type III—This is not commonly used in modern systems.

Type III uses four leads for supervision signaling: E, M, SB, and SG.

During inactivity, the E-lead is open and the M-lead is set to the ground connected to the SG lead of the signaling side.

The PBX (that acts as trunk circuit side) disconnects the M-lead from the SG lead and connects it to the SB lead of the signaling side in order to indicate the off-hook condition.

The Cisco router / gateway (signaling unit) connects the E-lead to the ground in order to indicate the off-hook condition.

E&M Type IV—This is not supported by Cisco routers / gateways.

E&M Type V—Type V is symmetrical and allows two signaling nodes to be connected back-to-back. This is the most common interface type used outside of North America.

Type V uses two leads for supervisor signaling: E, and M.

During inactivity the E-lead and M-lead are open.

The PBX ( that acts as trunk circuit side) connects the M-lead to the ground in order to indicate the off-hook condition.

The Cisco router / gateway (signaling unit) connects the E-lead to the ground in order to indicate off-hook condition.

Audio Implementation (two-wire / four-wire)
There are two distinct types of audio interface (two-wire or four-wire). These implementations describe the number of wires used in order to transmit audio signals.

With the two-wire implementation, full-duplex audio signals are transmitted over a single pair which consists of tip (T) and ring (R) leads.

The four-wire implementation provides separate paths to receive and send audio signals which consists of T, R and T1, R1 leads.

Note: Even though an E&M circuit can be called a four-wire E&M circuit, it is likely to have six to eight physical wires, based on the signaling type and audio implementation used.

Start Dial Supervision Signaling
Start dial supervision is the line protocol that defines how the equipment seizes the E&M trunk and passes the address signaling information such as dual tone multifrequency (DTMF) digits. There are three main techniques used for E&M start dial signaling:

Immediate Start—This is the most basic protocol. In this technique, the originating switch goes off-hook, waits for a finite period of time (for example, 200 ms), then sends the dial digits to the far end.

Wink Start—Wink is the most commonly used protocol. In this technique, the originating switch goes off-hook, waits for a temporary off-hook pulse from the other end (which is interpreted as an indication to proceed), then sends the dial digits.

Delay Dial—In this technique, the originating side goes off-hook and waits for about 200 ms, then checks to see if the far end is on-hook. If the far end is on-hook, it then outputs dial digits. If the far end is off-hook, it waits until it goes on-hook, then outputs dial digits.

___________________________________________
It works! Now if only I could remember what I did...
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[frigidzephyr]

Thanks guys, bas1234: that is pretty much just what I was looking for.

 

[kurthansen]

http://en.wikipedia.org/wiki/E&M

Wikipedia is a good search place also.

 

[SYQUEST]

Just a minor addition to what bas1234 posted. When interfacing a DS1 channel the configuration is "4Wire E&M", the audio being 4Wire and the E&M being anyone of the various types I thru V. The signaling states on a DS1 channel are handled by the A B C D signaling bits. Two for each direction of transmission. This way you can achieve three signaling states for full circuit supervision depending on how the channel unit is optioned for the service needed or equipment interfaced.

....JIM....

 

[Dexman]

If a circuit is optioned as SF, (Superframe) then the only bits that come into play are A & B. If a circuit is optioned as ESF (Extended Superframe), then the C & D bits will be used as well.

If it ain't broke, I haven't fixed it yet.

 

[frigidzephyr]

Thanks again guys for all the information.

 

[SYQUEST]

Dexman,

It has been a while, thanks for pointing that out. Most of the DS1s I worked with were SF/B8ZS or SF/AMI. We used ESF for data stuff at the time.

....JIM....

 

[Dexman]

SF/B8ZS???? Of all the circuits I've installed over the years, I think I've seen that combination only once!

If it ain't broke, I haven't fixed it yet.

 

[ISDNman]

Beware Cisco

They don't know telecom, so do NOT believe this verbatim, though it will certainly give you the general concepts.

In the past I have found inaccuracies, though I did not review this particular article.

The origins of the terms are vague and heance "earth and magneto" and "ear and mouth" are both common interpretations.

Real (analog) E&M signaling (which may be combined with either 2 or 4 wire audio)is very limited in terms of distance and was historically used for intra-CO switching machine connections.

However, the requirements for such connections (2-way and including passing digital strings) make it very useful.

In fact, on a non-PRI capable PBX E&M is pretty much the only way to do two-way DID.

If you ask a better question you will get a better reply. Be specific so we can help!

 

[SYQUEST]

Dexman,

The reason was 64k clear channel! You could do 64K DDS on SF/B8ZS without the expense of ESF hardware, etc. At one time ESF was more expensive. Northern Telecom added the B8ZS line code option to the DE4E channel bank's LDU. This way you could get full channel bandwidth. So I ordered most of our DS1s from the LECs as SF/B8ZS format. It did drive provisioning nuts at times, but it is an available option on the access side! The only switch that does not provide this is the GTD5 EAX. All you can get from it is SF/AMI, unless that changed in the last eight years.

ISDNman,

Cisco thinks they invented telephony! lol

In relation to the E/M issue at hand, telco over came the copper distance issue with DX signalling for most flavors of E/M types. But the advent of T1 in 1962 changed all of that for interoffice trunking.

When I worked at the paging company all of our microwave channels had E/M capability, although we did use SF (Singe Frequency 2600Hz) signalling on a lot of the voice channels.
We used Farinon and Collins 6gHz the microwave systems were analogue.

....JIM....

 

[Dexman]

Up until 3 years ago our IXC switches were DSC (now Alcatel-Lucent) DEX-600Es. The old DTFs were strictly SF/AMI unless you replaced the DTI cards with trunk cards manufactured by DGI.

Later on, DSC produced trunk frames that could be provisioned to support ESF/B8ZS. The last trunk frame produced was high density and the cards had on-board echo cancellation circuitry.

If it ain't broke, I haven't fixed it yet.

 

[PERRYPJ]

BACK IN RELEASE 17 THE ONLY OPTION YOU HAD FOR A ISDN-PRI WAS SF/B8ZS, IT WOULD NOT SUPPORT ESF

OLD ROLMEN WORKING ON NORTELS AND AVAYA

 

[PERRYPJ]

SORRY THAT WAS NORTEL MERIDIAN RELEASE 17

OLD ROLMEN WORKING ON NORTELS AND AVAYA

 

[SYQUEST]

I remember Release 17, and that explains why NT pushed that format. The M1/SL1 has supported ISDN-PRI for a long time...

....JIM....