“The key to success is action,

and the essential in action is perserveance”.

Since forming in 2002 PAVA Services have been trying to secure the work to upgrade this sites Voice Alarm system. And, the contract finally landed in April 2019.

Over the last year, PAVA Services has been hard at work upgrading the voice alarm system for one of the UK’s Nuclear Power Stations.

System Design.

The original system dated back to the 1970’s and was becoming increasingly difficult to maintain. Comprising mainly of True-Sound equipment, with modifications including a pair of Baldwin Boxall BVMX routers.

The constraining factors for any new design was the system architecture and consequently the loudspeaker circuits. An allowance for future expansion in the form of additional loudspeakers also had to be taken into consideration.

System Architecture.

The original system comprised of twenty-four 100W amplifiers connected in parallel. These, effectively, pool their individual output power into one output, sometimes called a parallel bank. Loudspeaker circuits connect via relays and tap off what power they need from the pool. Unfortunately, the load applied by the systems loudspeakers exceeded the 2400W it was capable of supplying.

Our philosophy was to produce a system whereby each amplifier drives only one circuit. Since the new amplifiers rated output would be 500W, each of the new circuits could not exceed that power rating.

In addition, the new system must be capable of supplying more power. Not only to cover the existing overload but also the increased load required by the additional loudspeakers necessary to improve site coverage.

This meant breaking down the loudspeaker circuits into smaller loads.

Loudspeaker Circuits.

Unfortunately, cost limitations prevented the installation of new loudspeaker circuits. Fortunately, the loudspeaker circuits had been run in four core cable; but crucially only two cores per cable had been used. This meant each cable had two spare cores. By rewiring some of the junction boxes we could easily double the number of loudspeaker circuits. Thereby reducing the load on each circuit.

Breaking the system down in to smaller circuits improves the systems overall resilience. If a loudspeaker circuit goes short or open it only affects that circuit. Simply, the bigger the circuit the more of the site it covers, therefore, failure of the circuit reduces the coverage in a larger area of the site.

One area posed a problem, the reactor building. A survey indicated that the area needed considerably more loudspeakers to improve coverage. There was no option but install a 19-core cable. As a result, the reactor building is now fed from seven circuits rather than just one.

The New Voice Alarm System.

The new system is based on Application Solutions (ASL) voice alarm equipment. Key to the design was the provision of a high degree of dual redundancy. In addition it had to incorporate the Administration Block and Contractors Area systems we installed in 2016 (see here more details).

Audio Routers.

Two Vipedia-12-net audio routers work in an Active/Standby pair to provide the dual redundancy of the systems routers.

The Vipedia’s provide the control/audio routing of the audio input sources and interfaces with the sites emergency systems. In addition, the Vipedia’s also take care of monitoring every part of the system, from microphone to loudspeaker.


The Vipedia’s handle inputs from three microphones: The Central Control Room (CCR); The Emergency Control Centre (ECC) and the site Reception Desk.

An ASL MPS10-AN-G0, is located in the Central Control Room (CCR). The microphone has two analogue audio outputs, with each output connecting one of the two Vipedia’s. For further resilience a hardware bypass ‘All Call’ fall back is also provided.

ASL MPS01-IP-G0 microphones are located in the ECC and Reception. These are an IP variant of the MPS01-AN-G0 microphone. It was necessary to install the IP variants to help keep costs lower since use of the site IT network obviated the need for new microphone cabling.

Alarm Interfacing

Alarm inputs are from switches on the CCR Desk, the Group 1 Alarm Cubicle and the Siren System connect to the system. Each input connects to both Vipedia routers via two digital interface units, one per router. As a result, this maintains the systems dual redundancy. In addition, fault monitoring of the alarm contacts ensures that the interconnecting cable is intact.

Operation of an alarm input broadcasts the relevant message or alarm tone across the site.

A non-urgent, off site, alarm is fed to the system via two Terracom TERRA-8IO units supplied by Penton UK. The TERRA-8IO devices allow the transmission of contacts over IP.


The new system is capable of providing four times the power of the system it replaces.

Two ASL D150, 150W amplifier modules and nineteen ASL D500, 500W amplifier modules provide the amplification. Six V2000 mainframes provide power supply and monitoring functions for the amplifier modules. Additionally, each mainframe also includes a standby amplifier.

The V2000 mainframes also house the loudspeaker circuit monitoring modules. The Vipedia system provides several line monitoring options which are programmable. Since the existing loudspeakers were being retained impedance monitoring is implemented.

The Simulator System

Finally, one further upgrade was necessary. The Simulator System. For training purposes there is a mock-up of the CCR which reflects the real CCR in look and operation.

The simulator, located off site, connects to the main site PAVA system. This allows control of emergency exercises from the simulator.

As a result, the microphone and amplifier in the simulator was changed. A Vipedia-12 and V2000 now sits at the end of the existing CobraNet link.


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Power Station Image: Rwendland, Heysham Power Station, from dockside, CC BY-SA 3.0