Gamma Horizon is the most deployed hosted business phone system in the UK — a position it has held for several years, reflecting a consistent track record of reliability, ease of use, and genuine fitness for the SME market. It is the system T2K recommends most frequently to UK businesses that want a fully managed cloud phone system without on-site hardware, complex IT involvement, or the risk associated with less established platforms.
Horizon runs entirely on Gamma's own UK network infrastructure, spread across multiple geo-redundant data centres. The 99.999% uptime SLA — equivalent to less than six minutes of downtime per year — is backed by genuine infrastructure investment. Administration is handled through a clean, web-based portal that non-technical staff can manage confidently. Adding users, changing call routing, setting up auto-attendant menus, and adjusting hunt groups are all straightforward tasks that require no technical background.
For businesses migrating off PSTN ahead of the January 2027 deadline, Horizon is one of the most straightforward migration paths available. There is no hardware to install at your site, the mobile app means remote and hybrid workers are covered immediately, and the admin portal gives you full control over your call routing from day one.
Use cases
Gamma Horizon is best for
✓
SMEs wanting a fully managed, reliable cloud system
Businesses of any sector wanting professional telephony without an IT function or on-site hardware to manage.
✓
Hybrid and remote workers
Staff who work from different locations benefit from Horizon's mobile app delivering the same experience as office-based colleagues.
✓
PSTN migration with minimal disruption
Businesses moving off traditional landlines before January 2027 wanting a straightforward, low-risk migration path.
✓
Multi-site organisations on a single system
Businesses with multiple UK offices can run all sites on one Horizon system with shared auto-attendants, call groups, and dial plans.
✓
Businesses without dedicated IT resource
The web-based admin portal requires no technical knowledge to use day-to-day.
Key capabilities
Core features
☁️
Fully hosted — no hardware
No on-site equipment to buy, maintain or replace. Gamma manages everything on UK infrastructure.
📱
Mobile app
iOS and Android app for calls, contacts and voicemail — same experience as a desk phone.
🔀
Call routing & auto-attendant
Build professional IVR menus, hunt groups, and routing rules through the web portal.
🎙️
Call recording
Available on higher tiers — call recording with browser-based playback and storage.
🔗
CRM integration
Salesforce, Microsoft Dynamics and other CRM connectors on higher service tiers.
🏢
Horizon Contact
Optional contact centre module for businesses with inbound call queue requirements.
Strengths
UK's most deployed hosted PBX
99.999% uptime SLA
No on-site hardware
Easy web-based admin portal
Strong mobile app
UK data centres only
Limitations
Cloud-only — no on-prem option
CRM integration on higher tiers
Teams integration via add-on only
Call recording not on base tier
Less suited to enterprise scale
Technical specifications
Full specifications
Deployment
Cloud only — UK data centres
User range
Any size business
Pricing model
Per user / month (tiered)
Mobile app
✓ iOS & Android
Video conferencing
Horizon Collaborate add-on
Call recording
Higher tiers
CRM integration
Higher tiers
Contact centre
✓ Horizon Contact add-on
Teams integration
Add-on available
Uptime SLA
99.999%
Data sovereignty
UK-hosted data centres
IT resource required
✓ Not required
PSTN replacement
✓ Fully IP-based
Side-by-side
How Gamma Horizon compares
Head-to-head comparison
vs Gamma Webex
Webex adds Cisco AI collaboration tools on top of Horizon's telephony. If your team needs video meetings, AI transcription, and unified messaging in one platform, Webex is worth the additional cost. For straightforward telephony, Horizon is simpler and cheaper.
vs 3CX
3CX requires more technical involvement and suits businesses comfortable with that in exchange for concurrent-call pricing and deployment flexibility. Horizon is right when simplicity, reliability, and minimal IT overhead are the priority.
vs Voiceflex Flow
Flow is stronger for Microsoft Teams-centric businesses and remote-first teams needing a UCaaS-first platform. Horizon is the more established, proven choice for general business telephony without a specific Teams requirement.
Gamma Horizon is backed by a 99.999% uptime SLA — less than six minutes of unplanned downtime per year. This is delivered through Gamma's own UK network infrastructure across multiple geo-redundant data centres.
Yes. Gamma Horizon includes a mobile app for iOS and Android that provides the same calling experience as a desk phone, including hunt groups, transfer, hold, and voicemail. Remote and hybrid workers have an identical feature set to office-based colleagues.
CRM integration — including Salesforce, Microsoft Dynamics, and others — is available on Horizon's higher service tiers. T2K can advise on which tier includes the integration you need.
Yes. Horizon is well suited to multi-site organisations. All locations run on a single system with shared auto-attendants, hunt groups, and call routing. Staff at different sites can transfer calls internally as if in the same building.
Yes — Gamma Horizon is a fully hosted IP phone system replacing traditional PSTN and ISDN connections entirely. It is one of the most straightforward PSTN migration paths for UK businesses ahead of the January 2027 switch-off deadline.
Further reading
Resources & related content
Guides, comparisons and case studies to help you go deeper on Gamma Horizon.
Speak with the T2K VoIP team for a no-obligation consultation, a tailored quote, and a clear migration plan. We handle everything from number porting to hardware and go-live support.
