The UK's Bridge to the
US Network.
Your US calls deserve to be answered.
Fuse 2 is FCC-authorised to sign
STIR/SHAKEN from the UK —
so you arrive as trusted, not spam.
AUTHORISED & ASSURED BY:
Fuse 2 was built on the conviction that UK businesses calling the US deserve to be heard, not filtered, flagged or silenced.
Around 73 million spam calls are made worldwide every day. US operators respond by labelling anything they can’t verify as “Spam Likely” — which is devastating if you’re a legitimate business ringing the US from abroad.
HOW WE DO IT
Powered by global certification, STIR/SHAKEN signing and
a network that makes UK numbers trusted in the US.
Our network is designed to cut through spam filters,
move faster than traditional carriers and
deliver the trust that US operators demand.
01
You place a call
You ring a US customer from your +1 number. Fuse 2 is the originating carrier — we know you, we know the number is yours.
02
We sign it
We attach a cryptographically signed token to the SIP INVITE, stamped with our FCC-issued certificate, declaring attestation A.
03
It rings trusted
The US carrier verifies the signature, trusts the origin, and delivers the call without “Spam Likely” — often with a verified tick.
Defined.
STIR +
SHAKEN
STIR
Secure Telephony Identity Revisited. The IETF cryptographic standard that defines how a call is signed: JWT tokens, ES256 signatures, certificates tied to phone-number ownership.
SHAKEN
Signature-based Handling of Asserted information using toKENs. The ATIS framework that defines how carriers use STIR in the wild: governance, certificate authorities, and the A / B / C attestation levels.
Together: a verifiable chain of trust that travels with every call.
A,B and C. The difference between ringing and blocked.
Every US call carries an attestation — a grade from the originating carrier signalling how confident they are about who placed it. A-level is the gold standard.
CARRIER ORIGIN
What Carriers See When Your Number Calls
TRUSTED
The carrier knows you, and that the number is yours
‘This is my customer. I gave them this number. This call originated on my network.’
- Highest possible trust score
- Highest answer rates in the US
- Eligible for the green "verified" tick on carriers that display it
- Signed at Fuse 2 origin — the A-level we offer
KNOWN BUT UNVERIFIED
Carrier knows the caller, not the number
“This is my customer. The call originated on my network, but I didn’t issue the number.”
- Used when customers bring their own numbers (BYON / whitelisted)
- Typically delivered, but may be analytics-scored
- Also offered by Fuse 2 for verified BYON scenarios
UNKNOWN
‘This call passed through my gateway’
“I don’t know the caller. The call entered my network from elsewhere – that’s all I can say.”
- What most UK / EU carriers provide
- High risk of 'Spam Likely' labels
- Frequently blocked outright by major US operators
Independently verified, at
A Level, on a live US call.
Here’s a real test call we placed from the UK to a US destination, verified through the ZipDX STIR/SHAKEN Confirmation & Debugging Tool – an independent third-party validator used across the US telecoms industry.
AUTHORISED
One of only a handful of UK carriers authorised to hold our own Service Provider Code token and sign traffic at origin — not through a third party.
A rare few
A + B
800K +
Stop Being Ignored.
Start Getting Answered.
Whether you're a UK contact centre, a B2B sales team calling into the States, or an international carrier reselling DIDs, our signing service plugs straight into your existing SIP setup.
Signed at origin
We sign every eligible call at A level on our own network — no third-party intermediary, no delegated signing, no broken chain of trust.
Full audit trail
Every signed call is logged with the PASSporT, timestamp, destination and attestation. Trace any delivery issue in minutes, not days.
Drop-in SIP trunking
Works with 3CX, MS Teams Direct Routing, Anywhere365, Genesys, and any SIP-capable PBX or contact-centre platform.
Global SIP, US numbers
Dial US destinations from anywhere in the world with US CLIs that ring as verified — powered by our PoPs in North America, Europe, Poland & Singapore.
KYC, built in
We know our customers and verify number ownership before issuing A-level attestation — the only way to sign legally, and the only way to stay that way.
Answer-rate uplift
Our signed traffic typically sees materially higher answer rates than unsigned routes — fewer “Spam Likely” tags means more conversations.
