What is CAS "MF" ?

[staticroute]

Hi All,

I went through an intensive interview this past Thursday on SIP and PBX to IAD integration. One of the questions that I failed on was:

You are trying to interface a Cisco 2821 with NM-HDV2 to a PBX via T1. There is a red alarm on both ends. You test both ends with a loopback and it comes up fine. The cable tested fine and has been verified to be a T1 cross cable. Changed out the cable, same thing. Put on a monitoring tool and nothing tells what the issue is. From a troubleshooting standpoint, what are things that should be checked considering all that has been done above?

Anyone have any ideas?

I answered all questions correctly but this one. He said he was pleased with my answers and gave me a homework assignment to work on:

- Research CAS - MF and how it applies to a customer PBX
- Research interdigit timers in CAS MF

He will give me a week to research this.

I have always dealt with CCS not much of CAS so this is why this is my weak point. I know MF stands for Multi Frequency, can someone give me a straight forward definition on how DTMF differs from MF?

 

[JcBWF]

channel-associated signaling

http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci1192947,00.html

- Channel-associated signaling (CAS) is signaling (for example, in a T-carrier system line) in which control signals, such as those for synchronizing and bounding frames, are carried in the same channels as voice and data signals. This arrangement is an alternative to CCS (common channel signaling) in which a group of voice-and-data channels share a separate channel that is used only for control signals




Perfection is expected, Excellence is Tolerated

 

[staticroute]

Thanks! I know what CAS is, it's just the MF part I'm baffled on. I know this has something to do with old legacy pbx's. How does it differ from DTMF?

 

[JcBWF]

Not positive, but think it stands for Medium Frequency. check wikipedia

Perfection is expected, Excellence is Tolerated

 

[nytalkin]

MF is Multi Freq used for inband signalling in CAS environments.

30 years and it's still true.....NO GOOD DEED GOES UNPUNISHED!

 

[staticroute]

Can DTMF be used in a CAS environment?

 

[ISDNman]

Hmmm,

MF trunks use an idle tone. This is the frequency of the infamous Captain Crunch Whistle.

I don't understand why the type of signaling would cause a red alarm. And a red alarm on both ends make no sense.

I think the MF issue is a red herring. Possibly both ends are set to use network clock?

Or the framing is set incorrectly?

Good luck