Connect a Grandstream DP-series DECT phone to a NumberGroup SIP trunk
Map your NumberGroup SIP trunk credentials onto a Grandstream DP750/DP752 DECT base — Profile holds the server, SIP Account holds the credentials, and Handset Line assigns it to a handset. Mapping table plus Grandstream's own guide.
This registers a Grandstream DP-series DECT base (DP750 / DP752, with DP72x / DP730 cordless handsets) to a NumberGroup SIP trunk. DECT differs from a desk phone: you configure a SIP account on the base station web UI, then assign it to a handset— so there's one extra step the desk-phone guides don't have.
When you ask us to set the trunk up, request Send Numbers As set to "United Kingdom" so Caller ID arrives in the familiar 01214001262 format on the handset screen.
The credentials and settings your device needs to register against the NumberGroup SIP trunk are:
- Domain / registrar:
sip.numbergroup.com - Authorisation ID (also called SIP username): looks like
T-AAAAAA-NNNe.g.T-102377-001 - Password: a random string we generate per trunk
- User-Agent Type: we set this our side to match your device (e.g. 3CX Phonesystem, DDI in R-URI (Asterisk), RFC3261 Standard Trunk) so DDIs present in the format your equipment expects
- Send Numbers As: also set our side — pick the format that works best for your platform:
- International (+xx) — true E.164 (
+441214001262) for 3CX, Cisco, Yealink and most modern PBXs - International (xx) — bare digits (
441214001262) for Asterisk / FreeSWITCH dialplan regex - United Kingdom — UK format (
01214001262) for direct-register desk phones / softphones where humans read the Caller ID
- International (+xx) — true E.164 (
- Allowed IPs (optional): for an extra security layer we can lock the trunk to only register from your office IPs — tell us which when you ask
Once you have the credentials, the rest of this guide walks through the device-side config. If you'd rather skip the config altogether, ask us — we'll do it for you on most common PBXs and phones.
Field mapping
Grandstream owns the click-path and keeps it current — the table below maps each NumberGroup value to its exact field, across the three layers a DP base splits config into: the Profile (the server), the SIP Account (the credentials), and the Handset Line (which assigns the account to a handset).
Browse to the DP base's IP from a computer on the same LAN. Config spans three areas: Profiles → Profile 1 → General Settings (set the SIP Server and Profile Active = Yes), DECT → SIP Account Settings (the credentials, bound to the Profile), and DECT → Handset Line Settings(assign the account to a handset's Line).
Full navigation is in the manufacturer's own guide: Grandstream DP752 / DP730 Administration Guide. We keep the click-path with them so it stays current — the table below is the part that's specific to your NumberGroup trunk.
| NumberGroup value | Grandstream DP-series field |
|---|---|
| sip.numbergroup.com | SIP Server (Profiles → Profile 1 → General Settings) |
| Profile Active | set to Yes (Profiles → Profile 1 → General Settings) |
| T-AAAAAA-NNN | SIP User ID (DECT → SIP Account Settings) |
| T-AAAAAA-NNN | Authenticate ID (DECT → SIP Account Settings) |
| your trunk password | Authenticate Password (DECT → SIP Account Settings) |
| select profile | Profile (DECT → SIP Account Settings) |
| UDP, RFC2833, codecs | SIP Settings / Audio Settings (Profiles → Profile 1) |
| assign to handset | set the account on Line 1 for the handset (DECT → Handset Line Settings) |
Don't skip the last row. If you configure the Profile and SIP Account but miss Handset Line Settings, the account registers fine but no handset can place or receive calls on it — this is the single most common DP setup mistake.
Split-field note: the DP splits SIP User ID from Authenticate ID. On a NumberGroup trunk both take the same value — your T-AAAAAA-NNN.
T-AAAAAA-NNN in both SIP User ID and Authenticate ID on one Account row, your trunk password in Password, and set Active to Yes. The numbers pictured are the vendor's example — use the values from the email we send you.Verify
- The base web UI shows the account registered, and the assigned handset shows a line/signal indicator
- We can confirm the trunk has registered our side — ring us or check the trunk-live email
- Dial your mobile from the handset to confirm Caller ID; ring your DDI from a mobile to confirm inbound
If it won't work
- Account registered but the handset can't call: you missed Handset Line Settings — assign the account to the handset's Line
- Won't register: wrong SIP User ID / Authenticate Password, or SIP Server not
sip.numbergroup.comexactly - Outbound UDP 5060 blocked on your network firewall
- Outbound rejected with 403: your Default CLI on the trunk isn't one of your DDIs — fix on the trunk
Set fraud caps before going live
A DECT base with a handful of handsets should be capped to your real peak. Ask us to set Fraud Detection Simultaneous Calls and a sensible Daily Spend ceiling. See our telecom fraud guide.
Cordless that just works
Members get SIP trunks with no per-channel fee and BT Wholesale call rates passed straight through — run your DECT handsets across the site on a modern carrier without replacing the kit.