Background

Live broadcast testing is one of the most intrusive aspects we undertake with PAVA systems. Test messages, pink noise and STIPA test signals for example, all result in a degree of annoyance to others around us. However, these broadcasts form part of the critical commissioning and testing process needed to assure the system’s compliance with the design and applicable standards. Despite the critical importance, we regularly find that our co-ordination with others is often met with an understandable reluctance or concern from station management, staff or local residents.

Intrusive Nature

Broadcasts are repeatedly activated, sometimes for long durations, and are usually conducted during the night.

As an example, Speech Intelligibility testing recently conducted at St Pancras station spanned two full night shifts to capture results from the 300+ test positions required.

Additionally, where people are subjected to continued high levels of noise, there is of course a potential to cause hearing damage. Maximum and average sound pressure levels have to be considered and mitigation measures put in place to keep people safe.

Concept

The team established that a bespoke mechanism for instantaneously and remotely triggering PAVA test messages & signals from a mobile device would be a major benefit. 

Design

A design criteria for the bespoke interface was established which included the following key aspects:-

·        Should not be constrained to any one PAVA system manufacturer or type.

·        Provide volt free and volt driven triggering options.

·        Not be constrained by distance between tester and the CER.

·        Allow any external voltage or ground source for triggering purpose.

·        Provide complete electrical isolation between the test equipment and system under test.

·        Must provide activation confirmations back to the remote user.

·        Provide clear status indication on both the mobile device and at the equipment rack.

·        Be able to operate entire shifts, even from standard domestic batteries.

·        Configurable broadcasting options and user interface to support any typical site.

·        Should only utilise low cost “jellybean” components, but without compromising any of the above.

Our solution development process involved integrating software coding with electronic circuitry design to create a user interface and control mechanism for the PAVA system under test. We conducted multiple bench test trials to investigate various solution options, culminating in the production of a prototype interface board that embodied the final concept.

PCB Design & Manufacture

The Bespoke Interface board was subsequently modelled using 2D/3D PCB design tool KiCAD and electronically submitted to PCBWay for manufacture.

The final board is DIN rail mountable and supports an optional 16X2 LCD interface display which provides additional status information and NTP synchronised clock functionality. 

Live Usage at Gatwick

The device has since been put to good use at Gatwick Station during pre-testing and Entry Into Service demonstrations for the new Station Entrance area. By utilising the remote triggering capability we were able to test each speaker operation in turn using short test message broadcasts of just a few seconds at a time.