Grandstream DP750, Incoming works, 503 on outgoing

Help & Support
1

Hey all. Trying to setup a Grandstream GP750 with my voip.ms service. It registers fine as seen both on the device itself and on my voip.ms account. I can receive calls fine, but I am unable to dial out. I get a 503 error on the phone as soon as it tries to dial a number. I’ve followed the wiki instuctions for the GP750, but even with that I can’t dial out. I’m sure it’s something dumb, but I can’t see what it could be. Any pointers?

2

Hello @ChinookTX,

Are you using SIP TLS? If no, do yourself a favour :blush:. If yes, are you sure you did setup the SRTP setting correctly (and “Force” it)?

I had to setup a DP750 a few weeks ago and I had to really dig in the menus here and there to get everything right. But I have no device in hand (nor a good memory) to help out.

I can only confirm that it works (I was using TLS/TCP) but I have to find the right option (especially the SRTP one I believe).

Kind regards!

3

Thank you for your response. I am using SIP TLS yes, and I configured my subaccount to encrypt calls, as well as my base station with TLS encryption. I got fedup this morning and deleted the sub-account and created a new one. It worked first time… There must have been something I changed way back that didn’t play nice with the DP750.

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4

Yes, it was not the easiest device to configure, but it finally worked. I am glad you could figure it out, somehow. :blush:

Kind regards.

5

As a side not on DP750, I would recommend not using the ‘parallel’ mode if you got several handset, I ran into some sneaky issues.

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6

I’m curious what problems you’ve encountered with parallel mode. It has been working fine for me for a few years.

7

Call transfer would randomly failed to connect. This was confirmed by support that parallel mode could cause such issue.

8

Ah! We have a small house, I usually just walk the phone over to the person being called. :wink:

9

Fixing the “Call Release [503]” Error on Grandstream DP720 with DP750 Base Station

I recently resolved the frustrating “Call Release [503]” error on my Grandstream DP720 handset paired with a DP750 base station. Like many of you, I could receive and answer incoming calls, but dialing out just wasn’t working.

Here’s what I did to get it up and running:

  1. Configuration using SRTP/TLS/TCP: I followed the instructions from the Grandstream DP750/DP720 wiki:
    hxxps://wiki[.]voip[.]ms/article/Grandstream_DP750/DP720

  2. Settings in VoIP.ms:

  • Enable Encrypted SIP Traffic: Go to Main Menu > Account Settings > Advanced > Encrypted SIP Traffic and set it to Yes, then click Apply.
  • Set CallerID: In Main Menu > Account Settings > Advanced > General > CallerID Number, choose Use one of my DIDs. (I mistakenly selected “I use a system capable of passing its own CallerID”.)
  • Update SIP/IAX Password: Navigate to Main Menu > Account Settings > Advanced > Security and set a new password under Main SIP/IAX Password. Make sure the new password contains only letters (A-Z) and numbers (0-9) - avoid special characters.

This solved the issue for me, and hopefully, it helps others facing the same problem!

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