What the Telstra outage actually showed
Telstra CEO Vicki Brady, returning from annual leave, faced immediate questions about a nationwide outage that had disrupted train services, payment systems, and access to triple zero emergency calls. The cause, as reported by The Guardian, was a software glitch — not a cyberattack, not a physical infrastructure failure, and not the result of staffing cuts (Brady was explicit on that point). Just a software error, propagating across an entire national network.
That’s worth sitting with for a moment. A single point of failure, at the software layer, took down services that most people assume are always available. Emergency call handling. Commercial payments. Public transport. These systems are operationally separate, but they shared enough common network dependency that one failure affected all of them simultaneously.
For anyone responsible for alarm signalling in the UK, the scenario maps directly onto a familiar risk.
Why this matters for alarm signalling
Alarm signals travel over networks. When those networks experience an outage – whether from a software fault, physical damage, or a carrier-level issue — an alarm signal that depends on a single transmission path may not reach the ARC. Depending on how the path is supervised, the first indication may be a communication fault rather than the alarm event itself.
This is precisely the risk that dual-path alarm signalling is designed to address. By providing two independent transmission paths, a properly configured system doesn’t rely on any single carrier or network technology being available. If one path fails, the second path maintains the connection.
Under EN 50136 and the grading requirements it defines, the expected transmission performance for higher-grade installations reflects exactly this logic. For higher-risk installations, EN 50136-compliant dual-path signalling provides the transmission performance and resilience typically required by the system specification.
The Telstra outage is a useful illustration of what that risk looks like in practice, at scale.
The PSTN transition makes this more pressing, not less
The UK’s PSTN switch-off – already underway with full completion expected by January 2027 – means that alarm systems previously running over copper telephone lines need to move to IP or cellular transmission. As AddSecure’s guidance on post-PSTN signalling sets out, that migration is an opportunity to assess the transmission architecture of each installation properly, not just swap one path for another like-for-like.
Installers who move a system from PSTN to a single IP path have technically migrated, but they haven’t necessarily improved the resilience of the installation. In some cases, IP paths can carry additional points of failure that PSTN didn’t – particularly if the broadband service and the alarm signalling both depend on the same router or ISP infrastructure.
The more appropriate approach is to treat the PSTN migration as the moment to establish proper dual-path signalling: one IP path and one cellular path, ideally using genuinely independent network infrastructure, so that a carrier-level event on either side doesn’t result in a silent installation.
What installers and ARCs should take from this
The Telstra outage affected emergency services, not just consumer apps. That’s the part that tends to land differently with people who haven’t thought through network dependencies before. Emergency infrastructure runs on commercial networks. Those networks can and do fail.
For UK alarm installers, the practical implication is worth spelling out plainly: every installation that depends on a single transmission path carries a risk that the customer may not fully understand. When a network goes down – even briefly, and for reasons entirely outside your control – the installation may lose its ability to transmit alarms.
Dual-path signalling doesn’t eliminate all risk, but it prevents the failure of one transmission route from becoming a complete loss of connectivity for the customer. That’s a straightforward conversation to have with any site owner, particularly as the PSTN migration prompts a natural review of how each system is connected.
ARCs, for their part, are well placed to reinforce this with the installer community. If an ARC can see which of its connected sites are running single-path configurations, that’s a meaningful contribution to reducing exposure across the whole estate.
Call to action
If you’re working through PSTN migrations and want to understand how dual-path signalling fits into your installations, speak to the AddSecure team. We can walk through the options for your specific site types and ARC requirements – no obligation, just a practical conversation.