GXW4200 feature request


For several reasons and the sake of older telephones working properly, I’d need the Advice Of Charge (AOC) information transmitted to the telephone connected to FXS.
These informations are sent using a pulse at 16khz or 12khz depending on the country.

To configure this, as this information can only be locally generated a textfield containing the config data. Example of config data:

The syntax is a series of semicolon separated AOC descriptions:

  1. frequency of tones (12k or 16k allowed only)
  2. Interval:Number of repeats
    2 can be repeated multiple times

AOC generation starts on on call connect.


16khz, charge one unit every 30 seconds, until end of call

16khz, first two minutes are charged each with a puls, then charge one unit every 30 seconds until end of call

12khz, first 300 seconds are charged with 1 units every 30 seconds, after this nothing will be charged anymore

12kHz, Charge one unit every minute

Having that feature would be a huge plus over other manufacturers and help a lot of people to solve some serious issues they have now, There was a manufacturer who implemented the functionality in sort of the described way but stopped supporting it, when a new HW release was launched.

Maybe you’d like to launch this feature with your new V2 HW generation.

Many regards


Out of curiosity, why would this need exist in a gateway whose only function is to convert a SIP signal into a analog signal? How would this translate into SIP for some billing purpose? It also seems that your request is quite specific to your need given that you wish to no longer charge after 5 minutes.


Let me put some light on this.

First, this does not translate SIP at all. It is only necessary to send those Signals to an analogue phone when the call is originated from it.

What do you mean by specific? The proposed syntax just allows that, the examples I gave are just some random examples which probably do not have much to with the real world but explain the syntax quite well (I hope).

Reason for that feature lies in the construction of older European phones and dialing systems. Before SIP and ISDN was established, the only way to detect reliably that a call originated from the dialing system has been answered was by reception of the first charge pulse.
So many alarm dialers, emergency call devices, notification dialers, automated industry, etc. still rely on that feature. The only way at the moment where this works well, is using a SIP-ISDN-Gateway which is able to provide AOCD information, set up very similar to the syntax above. To translate that into those 12 or 16 kHz pulses is to put a small ISDN PBX behind that gateway which is able to make those pulses from AOCD information (e.g. a small Agfeo PBX). As ISDN is fading in Europe as well, those PBXes get more and more unavailable on the market.

By the way, those dial systems still use pulse dialing, yes even nowadays. The elevators in the office building we are in, exactly use such a device in every cabin. Those emergency systems must not be changed (for regulatory reasons), otherwise the whole elevator system would need a complete overhaul. So the only way making these things work is the contraption described before. And that has its limits. As ISDN is providing two channels only, for six elevators, exactly three of these combinations are needed. With one spare one too, for the sake of security.

If we had the feature described above, we could just connect these six devices to the already existing Grandstream Gateway and save quite a bit of time and money as increasing the reliability.

And believe me, no one else has this feature this is why we are desperately looking for such a functionallity.

Many regards


I am just a user and was curious. GS will need to see the post, presumably do some cost analysis, determine the market need and then make a decision as to whether to proceed to incorporate the change.

You might ask others to vote the idea up so as to attract more attention.


Oh you are very welcome. Gave me the opportunity to explain that in detail.

So please - all readers who find this useful or interesting - join the thread :sunglasses:



Pushing up this topic as it gets more and more interesting. All other solutions start to disappear …