Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations Chriss Miller on being selected by the Tek-Tips community for having the most helpful posts in the forums last week. Way to Go!
E & M trunk connections PABX to PABX 2
- Thread starter satcom
- Start date
E&M is a real challenge, because there are many variations on the protocol, like how many wires are used (4 or 6), signallingtype (like wink-start), grounding etc.
Can you tell me more about what you're trying to do, and what equipment is used?
Also a Voltage/Resistance/Current device (how's that called in english?) can be handy, so you can measure what is happening on the wire's.
Cheers,
Nico
Can you tell me more about what you're trying to do, and what equipment is used?
Also a Voltage/Resistance/Current device (how's that called in english?) can be handy, so you can measure what is happening on the wire's.
Cheers,
Nico
- Thread starter
- #3
Further information. E&M type 5 at both exchanges, 4 wire E&M (7 or 8 wires in all). The question is really over the transition from E & M signalling to in-band tone signalling as the call progresses. CCITT R1 and R2 have differing MF tone definitions. If the connection can be completed with E & M pulse signalling only I would expect that the exchange to exchange dialogue can be achieved successfully - Can anyone confirm this?
Guest_imported
New member
- Jan 1, 1970
- 0
Is there a good website that explains E&M signaling?
-
1
- #5
satcom,
R1 and R2 signaling are completely incompatible. Are you trying to run R2 at one end and R1 at the other?
Normally, and E&M circuit is wink start, meaning that I wink my M lead, which you receive on your E lead. You then insert a tone detector to start receiving the digits that I will send. When you get a connection on your end, you bring your M lead high, which I receive on my E lead, and we consider call established.
The wink is used to reduce the likelihood of glare, or both ends attempting to originate on the same circuit at the same time. It woks in a manner very similar to the way ethernet networks handle collisions.
All that said, I have used pulse E&M once about a million years ago, and can't remember how it worked exactly, other than the fact that the call setup times are unreasonably long. It takes 1 second to pulse a 0, or at least 1/2 of a second if you can configure your equipment to do 20 pps.
You can send 10 digits MF in 1 second.
Where are you that you are using R1 and R2? These are old protocols and subject to toll fraud.
And for mitchld, the best E&M reference that I have ever seen was the manual for a Timplex Link/1, but that was back in the 80s when the only websites were on milnet and arpanet. And they were all text. But try this one and let me know if this is the level of detail that you are looking for:
pansophic
R1 and R2 signaling are completely incompatible. Are you trying to run R2 at one end and R1 at the other?
Normally, and E&M circuit is wink start, meaning that I wink my M lead, which you receive on your E lead. You then insert a tone detector to start receiving the digits that I will send. When you get a connection on your end, you bring your M lead high, which I receive on my E lead, and we consider call established.
The wink is used to reduce the likelihood of glare, or both ends attempting to originate on the same circuit at the same time. It woks in a manner very similar to the way ethernet networks handle collisions.
All that said, I have used pulse E&M once about a million years ago, and can't remember how it worked exactly, other than the fact that the call setup times are unreasonably long. It takes 1 second to pulse a 0, or at least 1/2 of a second if you can configure your equipment to do 20 pps.
You can send 10 digits MF in 1 second.
Where are you that you are using R1 and R2? These are old protocols and subject to toll fraud.
And for mitchld, the best E&M reference that I have ever seen was the manual for a Timplex Link/1, but that was back in the 80s when the only websites were on milnet and arpanet. And they were all text. But try this one and let me know if this is the level of detail that you are looking for:
pansophic
- Thread starter
- #6
pansophic
Thnks for that, I have already seen the reference, but also pleased with your response as it helps me formulate a clearer question or 2:
a) yes I understand that R1 and R2 are basically incompatible at several levels.
b) Several manufacturers make translation equipment at the E1 T1 trunk interface level but almost nothing addressing the analog trunk question. Is there a problem over E & M analog trunks?
I mentioned pulse dialling because in principle that would allow the call setup to be made without translation processes.
R1 embodies MF signalling rather than DTMF and uses different tone pairs to indicate digits or whatever. So even if the exchange to exchange connection is established over E & M lead DC signalling there appears to be an MF to DTMF mismatch.
Is this statement true?
Is there a conventional solution available without getting inside the exchange equipment?
Thnks for that, I have already seen the reference, but also pleased with your response as it helps me formulate a clearer question or 2:
a) yes I understand that R1 and R2 are basically incompatible at several levels.
b) Several manufacturers make translation equipment at the E1 T1 trunk interface level but almost nothing addressing the analog trunk question. Is there a problem over E & M analog trunks?
I mentioned pulse dialling because in principle that would allow the call setup to be made without translation processes.
R1 embodies MF signalling rather than DTMF and uses different tone pairs to indicate digits or whatever. So even if the exchange to exchange connection is established over E & M lead DC signalling there appears to be an MF to DTMF mismatch.
Is this statement true?
Is there a conventional solution available without getting inside the exchange equipment?
satcom,
As far as there being a problem with analog translation of R1 to R2, it is not that there is a problem, it is just not cost effective.
Actually, both R1 and R2 are MF signaling, they are just different types. If I recall, they are both 2 of 6 (meaning a set of 6 tones, with 2 of the 6 at any given time). This yeilds 15 distinct tone pairs. More than enough to represent the 10 digits that we allow, plus some to do nice things like a start tone and stop tone. There is also an SF (single frequency) tone that is present when the trunk is idle.
I'm not sure what you mean about the MF and DTMF mismatch. If you are using MF signaling to set up the trunk connection, you simply need to use the same signaling on each end. If you are concerned about the DTMF stations being able to access MF trunks, don't. The PABX collects the DTMF digits from the station, processes the call, and sends MF digits to the trunk.
Another option, potentially, is to allow users to seize the trunks directly by dialing an access level, like 8. Then the trunks can be set up for DTMF signaling, and the user can control them directly. For that matter, you could probably set up both PABXs to use DTMF signaling on the E&M trunks and just do it that way. Forget the carrier-class signaling altogether.
pansophic
As far as there being a problem with analog translation of R1 to R2, it is not that there is a problem, it is just not cost effective.
Actually, both R1 and R2 are MF signaling, they are just different types. If I recall, they are both 2 of 6 (meaning a set of 6 tones, with 2 of the 6 at any given time). This yeilds 15 distinct tone pairs. More than enough to represent the 10 digits that we allow, plus some to do nice things like a start tone and stop tone. There is also an SF (single frequency) tone that is present when the trunk is idle.
I'm not sure what you mean about the MF and DTMF mismatch. If you are using MF signaling to set up the trunk connection, you simply need to use the same signaling on each end. If you are concerned about the DTMF stations being able to access MF trunks, don't. The PABX collects the DTMF digits from the station, processes the call, and sends MF digits to the trunk.
Another option, potentially, is to allow users to seize the trunks directly by dialing an access level, like 8. Then the trunks can be set up for DTMF signaling, and the user can control them directly. For that matter, you could probably set up both PABXs to use DTMF signaling on the E&M trunks and just do it that way. Forget the carrier-class signaling altogether.
pansophic
- Thread starter
- #8
pansophic
Thanks for some sensible dialog, you are confirming my findings to a large degree, the big issue appears to be "can I force the PABXs at each side of the trunk to adopt a common protocol", both MF or both DTMF or whatever. There are some aging systems here, even the R1 protocol is "modified". However, I think our dialog has helped me formulate some questions for other contributers to a somewhat extended system, thanks again.
If I succeed I will let you know via this thread.
Thanks for some sensible dialog, you are confirming my findings to a large degree, the big issue appears to be "can I force the PABXs at each side of the trunk to adopt a common protocol", both MF or both DTMF or whatever. There are some aging systems here, even the R1 protocol is "modified". However, I think our dialog has helped me formulate some questions for other contributers to a somewhat extended system, thanks again.
If I succeed I will let you know via this thread.
-
1
- #9
jerryreeve
Vendor
Satcom,
stick in my two cents also for you:
1. MF was "Multi-Frequency" and designed for use between telephone switches, not at the user level. the digit stream for MF was ST M P NNX NXX XXXX SP (translates to ST-Start pulse M-Maintenance command P-Priority command(used in military AUTOVON, Commercial systems just inserted a 0) NNX-Area code, NXX XXXX-Office code and phone number, SP Stop Pulse) I do not have the Documentation with me at this time but i am very sure that the tones were from a two out of four tone generator (DTMF is two out of 8).
2. DTMF was as you know "Dual Tone Multi-Frequency" and designed for use at the user level ie. PBX, KSU, Telephone.
3. SF was signaling frequency and like stated above used to hold the channels idle when not in use and also to signal when a call ended and could be torn down. it made sense to leave the tone up because of the less than perfectly reliable analog trunks (microwave, cable, HF Radio, and others) that were the norm. when the SF dropped off without wink the tech was notified to check the trunk. SF came in a variety of flavors including but not limited to 1600HZ, 2250HZ, 2600HZ(Most common), and 2900HZ. The reason for E&M signaling along with the host of other items noted in this string was that while most telephone equipment and switches used 2 wires for talking the media for microwave and radio required a 4 wire connection, one pair transmit and the other pair receive.
JerryReeve
Communications Systems Int'l
com-sys.com
stick in my two cents also for you:
1. MF was "Multi-Frequency" and designed for use between telephone switches, not at the user level. the digit stream for MF was ST M P NNX NXX XXXX SP (translates to ST-Start pulse M-Maintenance command P-Priority command(used in military AUTOVON, Commercial systems just inserted a 0) NNX-Area code, NXX XXXX-Office code and phone number, SP Stop Pulse) I do not have the Documentation with me at this time but i am very sure that the tones were from a two out of four tone generator (DTMF is two out of 8).
2. DTMF was as you know "Dual Tone Multi-Frequency" and designed for use at the user level ie. PBX, KSU, Telephone.
3. SF was signaling frequency and like stated above used to hold the channels idle when not in use and also to signal when a call ended and could be torn down. it made sense to leave the tone up because of the less than perfectly reliable analog trunks (microwave, cable, HF Radio, and others) that were the norm. when the SF dropped off without wink the tech was notified to check the trunk. SF came in a variety of flavors including but not limited to 1600HZ, 2250HZ, 2600HZ(Most common), and 2900HZ. The reason for E&M signaling along with the host of other items noted in this string was that while most telephone equipment and switches used 2 wires for talking the media for microwave and radio required a 4 wire connection, one pair transmit and the other pair receive.
JerryReeve
Communications Systems Int'l
com-sys.com
jerryreeve
Vendor
Mis statement: MF was two of six tones not two of four JerryReeve
Communications Systems Int'l
com-sys.com
Communications Systems Int'l
com-sys.com
- Thread starter
- #11
- Status
Similar threads
- Question
