atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's Channel Bank FXO trouble with POTS lines

I can't seem to get the phone company to detect that the line has been picked up. My setup is like this:
POTS -> Adtran TA850 FXO -> T1 -> Phone System (Asterisk with T1 card).

For testing I did this to test my channel bank:

POTS -> TA850 FXO -> T1 -> TA850 FXS -> Extension.

When I go offhook at my extension I don't get dialtone. I have verified that I am sending the call to the correct channel over my T1.

Any ideas?

Just to follow up on this, another test that I did was to route the call coming in on the POTS line to music on hold(MOH) in my phone system:

POTS -> TA850 FXO -> T1 -> PBX(Asterisk) -> MOH.

My phone system sees the call come in, answers the call and sends it to MOH. When I place a call to the phone number of the POTS line I just hear ringing - as if the call hasn't been answered yet - even though my phone system reports that it has answered the call and has started MOH.

My phone system does detect that something is wrong and hangs up the channel. But, immediately it detects that the channel is still ringing so it tries to answer the call again.

SwampFox!

One step at a time... :thumb:

Reconstruct your circuit (while testing each phase) to precisely isolate your trouble to either POTS, the T1 (& FXO and FXS modules), or the Asterisk:

1. Fully test only POTS in front of the TA850 chasis that supports the FXO module. If successful, reconnect.

2. As mentioned in your first post, install the FXS module (and the T1) into an active TA850 chasis. From the chasis that supports the FXO module: Initiate an FXO module self-test, and observe the LEDs for any faults. If a normal condition is indicated by the FXO module's LEDs, perform your test again, this time from the CPE side of the FXS module.

3. If your tests are again successful at the CPE side of the FXS module, reconnect the T1 to the Asterisk and test.

Basically what 5E said. Start at the smart-jack, which is as simple as it gets, and test things going backwards. If your lights are green, and when your TA850 is plugged directly into the Smartjack (bypassing house wiring) and it works, then move backwards, adding in the house wiring. If it works still, then move back a step and connect Asterisk to the T1.

Out of curiousity, what type of T1's? Loop-start? Wink-start? Sounds like maybe you are recieving wink-start but expecting loop start maybe (if that's even possible). I'll let someone else answer that scenario tho.

Okay, the solution ended up being a lot simpler than I expected.

I called Adtran tech support and they suggested that I start swapping out parts, in particular the RCU and the PSU. When I swapped out the PSU on the channel bank with the FXO modules everything started working. I then noticed that the Ring Enable LED on the PSU was on and it hadn't been previously. After more testing with all parts I've concluded that the only problem was that the Ring Enable switch was not on and it should have been.

It's frustrating when you spend all your time checking software settings, cabling, parts, etc only to find out that you need to press a button on the front of the unit. ... Live and learn.

All is well now. Thanks for the posts.

Thanks for letting us know how it turned out.

Come back again,


Sam

A few questions.

Are the dial tone lines loop or ground start?

Is your Adtran 850 equipped with FXO channel units configured as POTS cards (Telcordia TR-08 standard), or as standard FXO using D type A&B bit signaling on the DSO bit stream?

There is a significant difference between each format.

Into what type of equipment does the T1 terminate into (D type channel bank or 1/0 DCS frame) at the far end?

If the far end is a LEC D4 type channel bank equipped with FXS channel units, you can not run the TR08 POTS signaling protocol.

Using a T1 test set capable of monitoring the T1 bit stream, and dropping out one of your FX channels with the capability to monitor A&B bit signaling, you should see the following:

Assuming Loop Start circuit operation with T1 SF.

FXO towards FXS:

Idle state (No ringing)
A/B = 0/1

Ringing state
A/B = 0/0

Talk State

A/B = 0/1

FXS towads FXO:

Idle State (On Hook)
A/B = 0/1

Talk State (Off Hook)
A/B = 1/1

If ESF, 16 state signaling is employed using A,B,C,&D signaling bits.

C bit will follow A bit. D bit will follow B bit.

If you have an NCI code associated with a LEC DS0 access circuit, it should be 02LS (Assuming a two wire interface at the far end). The FXO would hasve the equivalent to an NCI code of 02LO.