Many housing providers are well aware of the digital switchover and how this affects their telecare services. But the impact of the upcoming ISDN withdrawal has been less publicised. This is also significant as it’s likely to lead to a spike in first time call failures if key issues aren’t addressed. What does this mean in practice and what questions do you need to ask your monitoring centre?
The ISDN withdrawal is potentially problematic because the majority of monitoring centres currently use this technology to receive telecare alarm calls. They will therefore need to replace ISDN very soon.
But ISDN plays an important role for those telecare services still relying on analogue equipment. It’s helping stem the tide of analogue and digital compatibility issues, essentially bridging the gap between the two technologies.
This means monitoring centres using ISDN may not have felt the full impact of the digital switchover so far – and it’s the main reason why a failing analogue device might work at one monitoring centre but not another.
When ISDN is replaced, these compatibility issues will no longer be masked and there’s a strong likelihood we’ll see a huge increase in first time call failures as a result.
What is the ISDN withdrawal?
ISDN (Integrated Services Digital Network) delivers both voice and data over the telephone network. It’s an ageing technology and is being replaced by solutions that send voice and video calls over the internet.
The withdrawal of ISDN is separate, but linked to, the digital phone switchover. It’s following a similar timetable, with BT confirming: “We plan to have moved everyone over before Openreach stop the PSTN (and ISDN) service by 2027.”
In fact, some telecom providers have notified larger telecare service providers that the withdrawal process will begin at the end of 2024.
How does the ISDN withdrawal affect telecare services?
Monitoring centres will need to find a replacement for ISDN. This is most likely to be in the form of Session Initiation Protocol, or SIP, trunks, which use an internet connection to carry voice calls.
SIP trunks support both voice and data, offering high levels of reliability, but they behave differently to ISDN. Some telecare systems and equipment may not be fully compatible with SIP trunks.
How telecare alarm calls are sent and received
The problem lies with telecare services still using analogue equipment designed for the telephone network.
When an alarm call is triggered, it’s sent as an analogue signal – typically dual tone multi frequency (DTMF) – which is a series of audible tones and pauses. The signal is sent to the monitoring centre via a single channel along with the data from the alarm call, using a communication method called in-band transmission.
ISDN has been able to deal with this. But SIP trunks favour out-of-band transmission for DTMF data, which separates the signal into a side channel in a digitised format. It’s a more efficient way of handling data, making it less susceptible to corruption or delay.
An analogue signal needs to be converted to digital for out-of-band transmission, so the SIP trunks can process it correctly. If the signal is left in-band it’s likely to be corrupted. As most monitoring, centres have no technology to mitigate this, they just reject the call.
In addition, there’s a set of rules for translating analogue signals into a format that digital systems can understand. This is called RFC 2833 but not all monitoring centres support this.
How can you reduce the risks of the ISDN withdrawal?
If SIP trunks are installed without significant adjustments, the industry will see a huge spike in first-time call failures – as much as 85 percent of calls failing first time. This will increase the time it takes to connect a telecare alarm call, delaying the response or even causing the call to fail completely, putting people at risk.
So, what should you do to prepare for the ISDN withdrawal and limit a rise in your call failure rates?
Ask your monitoring centre:
- Are you using ISDN and have you received notice of withdrawal yet?
- Have you tested SIP trunks on your platform to check for compatibility issues?
- What’s your plan to deal with this?
Our goal at Appello is to provide all the facts on the digital phone switchover, so you can make decisions with confidence. Talk to us about your next steps for a pain-free transition to digital telecare.
