Most lines are loop start. I have never seen an ATA that could do ground
start.
Ground start was used by some PBX systems. The PBX would put a ground on
the tip side of the line telling the central office to send dial tone.
If it works at all, it is working. You may have some RIP silence timer type
of problems.
And, if the line voltage is low, some things can get unhappy. Check the ATA
voltage on the pair when it is not off hook.
Some PBX type of equipment and older fax machines wanted to see -48 volts
nominal on the open line.
And, interrupting loop current is a way for a central office to force a
disconnect. If your voltage is too low, the PBX may think you are sending a
disconnect. And the ATA is probably not interrupting loop current when the
line disconnects from the far end.
You may be sending data. Caller ID comes in a burst of Bell 202 FSK
modulation. It sounds like data to a telco guy and in fact it is data.
You may want to upgrade your SIP equipment. I am sure somebody like Adtran
or perhaps Tellabs has a carrier class ATA. This one says it has -48 Volts
on the loop:
http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cata/187/1_0/english/administration/guide/sip/187adm80/a187_agCspc.html
-----Original Message-----
From: Nate Burke
Sent: Tuesday, February 17, 2015 4:24 PM
To: Animal Farm
Subject: [AFMUG] OT: Types of Telephone lines
I'm trying to hook an ATA (Grandstream GXW4004) up to a Mitel PBX. The
Mitel is expecting a 'Loop Start' line. I've read through the Wikipedia
pages, and looked through the documentation. But I'm still confused.
How do you tell if an ATA is producing lines that are 'Loop Start' or
'Ground Start' Or is there something else it's doing.
The client is having issues where some calls are terminating in the
middle of a conversation, or not disconnecting and leaving the line
open. The PBX Contractor (the only way you can do anything with a Mitel
PBX is through a Contractor) is telling them that they can make no
adjustments to the analog card in the Mitel, and it's not working
because our lines are 'Not up to industry standards for loop start
lines.' When they had ILEC POTS lines, the PBX was working normally,
this just happened when we switched them to an ATA.
I have a ticket open with Grandstream, but I thought I'd ask here. Is
there a way to test loop vs Ground start, and verify that the ATA is up
to 'Industry standards'? The Contractor is Telling the client that our
lines have low voltage, and there is "data" present on the line. I
wasn't on site when the tech was, so I have no idea what sort of testing
he was doing.
Any telephone guys care to offer insight?
Thanks,
Nate
