Add mobile + push to any PBX.
Spanvox gives ITSPs and PBX vendors a beautiful native softphone, reliable push for incoming calls, and NAT traversal, bridged to the phone system you already run. No trunks. No dialplan changes. Sold under your brand.
- No SIP trunks
- No dialplan changes
- Push that wakes
- Works behind corporate firewalls
- Encrypted end to end
- Any SIP PBX
Bridges to the SIP PBX or softswitch you already run
One bridge. Two registrations. Zero PBX changes.
Spanvox keeps a live registration to your PBX on each endpoint’s behalf, and a push-driven registration from the app. To your switch we’re just a softphone, so mobile, push and NAT traversal need no trunk, firewall rule or dialplan edit.
Registers with the credentials we mint, on our domain. Never sees your PBX password.
- downstream app, encrypted
- upstream to your PBX
- media media proxy anchor
- push wake on incoming
Sees an ordinary registered softphone. Keeps its numbers, dialplan and PSTN, with no changes.
- 1
Your backend calls
POST /v1/endpointswith the extension’s SIP credentials on your PBX. - 2
Spanvox stores the upstream creds encrypted and mints separate downstream app credentials on our domain.
- 3
Our SBC registers upstream to your PBX on the endpoint’s behalf, so you just see a softphone.
- 4
The device registers downstream to Spanvox. Both legs are live; the bridge is up.
- 1
A call your PBX routes to that extension arrives at Spanvox, which holds the upstream registration.
- 2
App asleep? Spanvox push-wakes the device over APNs/FCM while the INVITE waits.
- 3
The device reconnects, re-registers downstream, and CallKit / ConnectionService rings natively.
- 4
Our media proxy bridges and transcodes media across both legs: HD audio, NAT traversed.
- 1
The user dials from the native app, authenticated by digest against Spanvox.
- 2
Spanvox forwards the call out through that endpoint’s upstream registration to your PBX.
- 3
Your PBX runs its own dialplan and owns the PSTN, numbers and routing, unchanged.
- 4
Our media proxy anchors media; STIR/SHAKEN and caller-ID headers pass through untouched.
A global anycast backbone, encrypted end to end
Every session rides a multi-redundant anycast network and is secured with end-to-end encryption, so calls connect fast and stay private wherever your users are.
- 350+
- major cities on our anycast backbone
- 99.99%
- uptime target, multi-redundant by design
- E2E
- encrypted signalling and media
- 0
- trunks or dialplan changes to go live
A provisioning API that gets out of your way
Spanvox is API-first. Your platform stays the source of truth: call us to create endpoints, and we handle registration, push and media. Clean REST, predictable envelopes, idempotent writes.
One call to onboard a user
POST your extension’s SIP details. We mint app credentials and start bridging both legs immediately.
Secrets never leak
Upstream PBX passwords are AES-GCM encrypted and never returned. Devices get a one-time token or QR.
Idempotent + webhook-driven
Safe retries with Idempotency-Key, plus signed webhooks for registration, CDR and reachability events.
# Provision an endpoint: start bridging
curl -sS https://api.spanvox.com/v1/endpoints \
-H "Authorization: Bearer sk_live_K9xZ…" \
-H "Idempotency-Key: acme-user-1001" \
-d '{
"sip_domain": "acme.spanvox.com",
"caller_id": "+15125550123",
"upstream": {
"server": "pbx.acme.com",
"r_username": "1001",
"password": "••••••"
},
"downstream": { "delivery": "token" }
}'{
"ok": true,
"data": {
"endpoint_id": "ep_lt0k9f3a1b2c",
"app": {
"sip_uri": "sip:[email protected]",
"provisioning_token": "prv_8Q4…",
"transports": { "wss": "wss://sbc1.spanvox.com:8443" }
},
"upstream": { "reg_status": "pending" }
}
}The hard parts of mobile VoIP, handled
Push, NAT, network handoff, identity, fraud: the things that make “put our PBX on a phone” a multi-year project. Spanvox ships them as one platform.
Native on every device
Genuine native apps for iOS, Android, Windows and Mac: one infrastructure across all of them. Calls ring through the OS (CallKit, ConnectionService), never a web view.
Push that actually wakes
VoIP push over APNs/FCM with TTL≈0 so calls ring instantly and stale pushes never phantom-ring. Presence-following with a 5-minute grace.
Connects on any network
A managed media proxy anchors every call, with TURN on Cloudflare’s anycast edge over 443. If a device can reach HTTPS, it can call, even on locked-down corporate Wi-Fi.
Global anycast backbone
A multi-redundant anycast backbone spanning 350+ major cities routes every session to the nearest edge, with automatic failover and no single point of failure.
Bring your own PBX
Bridge to Asterisk, FreeSWITCH, 3CX or any SIP switch. We register like a softphone: no trunk, no firewall rule, no dialplan edit.
BYOD SIP, day one
Desk phones, ATAs and third-party softphones register directly and get the same bridge: persistently, no push needed.
PBX voicemail integration
Unanswered calls fall back cleanly to your PBX, so your existing voicemail, find-me / follow-me and IVR keep working, untouched.
SMS & RCS messaging
Reach customers beyond voice. SMS and RCS business messaging run through the same app and the same tenant, ready to switch on.
Seamless network handoff
Walk out the door on Wi-Fi → 5G mid-call. The app re-anchors and the media proxy latches the new path: no one-way audio, no dropped call.
STIR/SHAKEN passthrough
We proxy inbound and never rewrite the identity. Caller-ID, attestation and verification headers pass through untouched, so verified calls stay verified.
Toll-fraud protection
Toll fraud is every ITSP’s number-one worry. Per-endpoint concurrency caps, registration rate-limiting and automatic IP banning contain abuse before it ever reaches a bill.
Encrypted end to end
A Session Border Controller with TLS/WSS signalling and SRTP/DTLS media, encrypted end to end. Credentials are encrypted at rest and never exposed to the device.
One platform. Infinite brands.
Multi-tenant from day one. Spanvox is the engine; your customers only ever see you: your name in the store, your colours in the app, your domain on every registration.
Full customisation
Your logo, colours, typography and the entire look and feel. The app is unmistakably yours, top to bottom.
Languages & RTL
Ships multi-language with full right-to-left support: English, Arabic and Hebrew today, more on request.
Domains & push identity
Per-tenant SIP domains, or your own custom domain, plus your APNs and FCM credentials, so every call runs under you.
Your store listing
Ships under your Apple Developer account and Google Play: your bundle id, your name, your reviews.
A mobile product, without re-platforming
Keep the switch you’ve invested years in. Spanvox bolts on the modern client layer your customers keep asking for, and gives you an API and dashboard to run it at scale.
Zero reconfiguration
No SIP trunk, no firewall changes, no dialplan edits. We register to your switch per endpoint, like any softphone would.
Metered per tenant
Billed by seats or concurrent channels, never per-minute. You keep your numbers, your PSTN and your margins.
Full visibility
Both registration legs, live devices, CDRs with MOS, audit logs and signed webhooks, across every endpoint, in one place.
An app people actually want to use
Behind the scenes it’s a registration bridge. To the person holding the phone, it’s simply the best softphone they’ve used: fast, native and reliable.
-
Rings instantly, even asleep
VoIP push wakes the device and CallKit rings before the call even connects. No “missed while backgrounded”.
-
Feels like the phone, not an app
Native call UI, your contacts, recents and voicemail. It behaves exactly the way people already expect.
-
HD audio that survives the commute
Crystal-clear Opus, and calls that hand off cleanly from Wi-Fi to cellular as you walk out the door.
-
One identity, every device
The same line on iOS, Android, desktop and desk phones. Switch seamlessly, never miss a call.
Priced to scale with your seats
Metered per tenant, by seats or concurrent channels, never per-minute. You keep your numbers, your PSTN and your margins. Start free, talk to us when you go live.
Sandbox
Build and test against the full provisioning API.
Start building- Test API keys (sk_test_…)
- 1 SIP domain, up to 5 endpoints
- Full registration-bridge flow
- Provisioning tokens & QR
- Community support
Growth
Go live with white-label apps for your customers.
Talk to sales- Production endpoints at scale
- Your APNs / FCM push identity
- Multiple SIP & custom domains
- Signed webhooks + CDRs
- Native iOS & Android apps
- 99.9% uptime, email support
Enterprise
Dedicated capacity, residency and white-glove onboarding.
Contact us- Dedicated SBC nodes
- Multi-region media + GeoDNS
- EU data residency & DPA
- SSO + audit exports
- App-build pipeline & store submission
- Priority 24/7 support + SLA
All plans include TLS/WSS-only signaling, SRTP media, NAT traversal and anti-fraud controls.
Add mobile to your PBX in days, not years
Tell us your switch and your brand. We’ll get you an API key and a working bridge to a test extension, then native apps under your name.
Or email us at [email protected]