CRC on Bc9 Q-sig

[Nibbio]

What's the command to set CRC4 on or off in MD110?

 

[whosrdaddy]

there's no command, the TLU76 will follow automatically what is set on the other side...

-----------------------------------------------------
What You See Is What You Get
Never underestimate tha powah of tha google!

 

[fouesnant]

Hi
you can do a SACOS
SACOS:UNIT=SLP60,LIM=xx,ADDR=909,SECTOR=REL,DATA=yy;
yy as the following values
01 = "AUTOMATIC CRC-4" MODE !
11 = "NO CRC-4" MODE !
31 = "ALWAYS CRC-4" MODE !

In BC9, it is valid for all TLU76/1 or TLU64 using SLP60 signalling scheme.
So if you have QSIG and Public line in the same LIM, the CRC4 procedure will be applied for both
In BC12, you can separate, DSS1, Public and QSIG.

 

[HIREI]

Hi, whorsdaddy,
but if two MD110 with automatic detection connected? What is preferred?

........ and, pls, how to translate "...tha powah of tha google! " (powah - power? tha - ...);

Thanks

 

[fcpli]

fouesnant!
What's the idea to change CRC, if MD does it automatically? In my experience, the problem is ALWAYS on the other side, PSTN or whatever.....
Consider carefully why you want to change the CRC manually before doing anything!
The sacos command is not relevant to use in a PBX which is connected to a PSTN, it does NOT help (except the PSTN is not an old pre-war version)!!!

 

[fcpli]

Sorry, I forgot to mention that SPECIALLY between to MD's, DO NOT TOUCH THE CRC, it is automatic, as Daddy wrote.
Maybe you have sync. problem or something like that - in any case, the CRC value changes do not help, vice versa.

 

[IPuser]

Just note if your messing with CRC-4 On / OFF at the other (non-MD110) end. If you change it, the Automatic detectionm on MD110 won't necessarily pick it up, So you could get errors reported, until you restart the board.

 

[fouesnant]

Hi fcpli

The idea of changing CRC4 was that our PSTN does not support automatic CRC4 detection and that it must be set to no CRC4.

Secondary, we have operators as customer that request to set CRC4 to no automatic detection.

I don't know if it is old pre-war releases PSTN, or if it is the way they choose to implement the connexion, but it is like that.

In other hand, why is there the possibility to modify CRC4 in the MD110 SW?
Can anybody tell me the real use of CRC4 ?

 

[HIREI]

Hi, all,
I think, fouesnant is right, in a way. MD110 is small AXE. In a real AXE we have dtidp / dtidc commands:
CRC=0 - no CRC4;
CRC=1 - sorry, I can't understand it ;
CRC=2 - yes CRC4;
CRC=3 - automatic adjustment for CRC4.

Use of CRC4 - deeper analysis of errors and other things.

 

[Nibbio]

Ok. The problem is: I have a Md110 (BC9) connected to Tenovis Integral 55 with Q-sig link. Integral side I can verify that CRC in on, but what about Md?

I dont' need to change CRC but I need to be sure that is ON!!

 

[fouesnant]

Hi

Then do
SACOP:UNIT=SLP60,LIM=xx,ADDR=909,SECTOR=REL;
and verify the value at the address compare to the table os possibles CRC4 values :
01 = "AUTOMATIC CRC-4" MODE !
11 = "NO CRC-4" MODE !
31 = "ALWAYS CRC-4" MODE !

Normally by default it should be set to automatic, unless your country parameter is configure to sometihng else.

 

[Couler012]

Hi all!

Do anyone know how to change CRC-4 in BC10 for unit SLP60?
I need to override the automatic setting.

 

[fouesnant]

Hi

In BC10 try
sacop:unit=slp60,lim=1,filno=12,point=0&&3,reloff=791;
To view the change :
irpdprot=qsig,type=sl60,lim=1,entry=crc4mode;
irpdprot=etsi,type=sl60,lim=1,entry=crc4mode;
irpdprot=nat,type=sl60,lim=1,entry=crc4mode;
irpdprot=res,type=sl60,lim=1,entry=crc4mode;

The pointer were you change the value in Hex is printed in decimal with IRPDP.

Best regards

 

[testcentre]

Fouesnant

In response to your question about the purpose of CRC4, the following may assist.

With the introduction of ISDN it is possible for users to transmit data over a 64 kbit/s clear channel. The problem with this is that it is possible for user equipment to transmit the bit pattern 10011011 which corresponds to the 2 Mbit/s Frame Alignment Signal. PCM links with CRC4 overcome this possibility by checking first that the Frame Alignment Signal is correct, then checking that the CRC4 Multiframe signal is correct before allowing 2 Mbit/s link synchronizing. CRC4 also increases the likelihood of detecting errors in the 2 Mbit/s stream. This is most important as the signalling transfer for the D-channel is at a 64 kbit/s rate which means each bit corresponds to just 244 ns on a 2 Mbit/s link! It is very easy for this to be corrupted by noise unlike with Channel Associated Signalling where bit patterns only change every 2 or 4 ms.

 

[fouesnant]

Hi testcentre

Thanks for your analysis.

 

[Couler012]

Hi fouesnant!

Thank you for the valuable information.