Video Transcript
Analog Telephony (Part 3)
6m 13s
00:07
We’re back.
00:08
Alright, let’s wrap up with what happens when we’re in a call, incoming calls, hang ups,
00:13
and then a few troubleshooting techniques.
00:15
When we're in-call, we want to see two things.
00:19
We want to see a fairly stable voltage here and a stable current.
00:23
Sometimes when we don’t have great wiring or things are a little weird
00:27
and you're dropping calls or having other issues,
00:30
it really comes down to this line, the voltage current relationship.
00:35
Make sure to verify that there's not an intermittent short or some kind of other condition.
00:40
Often times when all the telephony wires come back, they come back to these punched down blocks,
00:46
so make sure to check the wiring in there when you're having problems
00:49
Toggle back to the control tab and let's look at hangup detection.
00:53
Loop drop is for real CO lines, if you will, that come from the telephone company.
00:59
Sometimes if all you have is the call progress, the problem is that the call progress is the reorder tone.
01:05
So you might hear that in the room before it auto hangs up.
01:09
And unfortunately there's not a lot you can do about this when that happens.
01:13
Here’s another hot tip for interfacing in-house PBX systems:
01:17
they don't always use standard call progress tones... unfortunately.
01:22
For example, the Siemens PBX might use German signaling rather than American signaling.
01:28
As a result, you may need to adjust the country in the Core properties
01:32
when you're using a private branch exchange.
01:35
Since we're internal, they don't need to follow the rules of the external country.
01:40
When it comes to incoming calls, it’s important to note line voltage is DC measurement.
01:46
As we discussed earlier, ring voltage is AC voltage, so it wont be reflected in this measurement.
01:53
It might be necessary to confirm incoming ring voltage with a voltmeter attached to the circuit.
01:58
When there is an incoming call, you simply see incoming call and caller ID in the progress string.
02:05
The ringing LED will strobe, and it strobes for the duration of the ring cadence.
02:10
Remember…if you don't enable a tone in the control tab,
02:14
then you won’t hear any indication that there’s an incoming call.
02:17
As we explained earlier, the interface does not play DTMF tones dialed by the user into the room.
02:24
Some users insist they want to hear them. QSC support can provide a user module that will accomplish this task,
02:32
but we’d like to avoid it whenever possible.
02:35
And if you're going to use it, make sure the tones are fed into the AEC reference of the microphones
02:42
to minimize the chances of ‘double-tap’.
02:44
When integrating Q-SYS call control to an external control system,
02:48
there are some potential problems you want to avoid.
02:52
Number one:
02:53
Many times a control systems programmer will only create a named control for the Dialer’s ‘dialstring’ field.
03:01
That works perfectly for the initial dial process,
03:03
but the keypad button controls MUST be used to dial any in-call digits so you need to create named controls
03:11
for all the keypad buttons as well as the other call control buttons to make use of all functionality.
03:18
Remember the keypad numbers and the other call controls are ‘trigger’ type controls.
03:24
If they’re treated as momentary or toggled controls in the control system,
03:28
you're going to have some pretty strange results, and I don't think it's going to work the way you envisioned.
03:34
So, don't do it!
03:36
Another common problem is the use of the ‘ringing’ or ‘off hook’ led signals
03:41
rather than using the dialer's control progress field as the only indicators of call status.
03:47
We really recommend you create named controls for the call progress fields and then parse that
03:53
out into the control system to have good data on the status of the telephone interface.
03:58
Earlier we mentioned the need for analog telephone adapters or ATAs.
04:04
For example, maybe you're using a hosted solution, that doesn't support Q-SYS softphone interface.
04:10
Very often they'll just send an ATA that's already set up and if you can't get proper signaling on the other side,
04:16
then it's very hard to know, if you have a VoIP problem or an analog telephony problem?
04:23
Based on which ATA you're using,
04:25
sometimes they can push the boundaries when it comes to electrical properties.
04:29
These are typically low power devices,
04:32
which makes it difficult to reproduce signals generated by the CO.
04:36
There are a few that we recommend in our documentation.
04:40
When troubleshooting, it’s often good to have a simple phone that you can connect to the analog side
04:46
to verify VoIP operation even before you get Q-SYS involved.
04:50
Also remember that it’s important to have the correct ATA…
04:54
The ATA needs the FXS port to interface properly with the Q-SYS POTS.
05:00
When troubleshooting these or other POTS related issues,
05:03
it’s useful to know the tolerance of the Q-SYS POTS interface.
05:08
For example, line voltage needs at least 18V DC on hook and 3 V DC off hook (with a nominal 6 VDC).
05:17
You got similar scenarios for Line current and ring voltage,
05:20
so I would take a good hard look at this slide and make note of these requirements.
05:25
Let’s say you’re having a problem with Q-SYS telephony
05:28
and you see what seems to be good levels and signaling in general.
05:33
For cases like this,
05:34
we’d recommend taking a few steps and gathering some information for the Q-SYS support team.
05:39
Number one:
05:40
Enable the POTS event logging, and then add recorders and record the POTS receive signal.
05:47
Then, make any successful or unsuccessful types of calls.
05:51
Then extract the Q-SYS log archive from the Core Manager and recorded audio files.
05:56
This data, and a good explanation of the problem,
06:00
can help your Q-SYS support team resolve the issue sas quickly as possible.
06:04
That’s it for Plain Old Telephone Systems from your Plain Old Training Guy. We'll see you next time.
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Analog Telephony (Part 3)
6m 13s