Automation of lighthouses began in Scotland as early as 1894, when Oxcars in the middle of the River Forth, just off Granton, had its two lightkeepers withdrawn. The light was operated using gas delivered weekly from Granton Gasworks and controlled by a clockwork timer to turn the light as required. An attending boatman delivered the gas from Granton and wound up the timer during a weekly visit.

The impetus for automating lighthouses in this period came as a result of the high costs in manning in excess of 90 Lighthouses. It should be noted that over 100 Minor Lights also existed that were unmanned from build but these were small structures, usually less than 7 metres high, that had light ranges of less than14 Miles.

Gas operated lights were installed to Automate manned Lighthouses from 1960 to 1980. The gas pressure was used to power a mantle giving a very bright light. The gas pressure was also used to rotate a lens around the gas mantle at the focal point of the lens. Such equipment was able to provide the 18 Mile plus ranges of Major Lights.

This was the first major phase of automation of lighthouses in Scotland and involved approximately 25 stations.

It is possible that more installations would have been automated much earlier had there not been Fog Signals and Radio Beacons present at many locations.

With advances in technology, the provision of automatic fog signals and reliable offshore power supplies operating to better than the International Association of Lighthouse Authorities (IALA) standard became possible and the automation of the remaining 65 Major Lighthouses took place from 1980 until completion in 1998, when Fair Isle South became NLB’s last manned Lighthouse. During this final era of automation, the development of monitor systems enabled all Major Lights to be supervised from NLB Edinburgh using radio and telephone.

Solar power also became an option during this period but was not extensively used as lamp technology had not yet yielded the benefits which are now available. All of the previously automated gas lights have now been solarised.

Before the automation of major lighthouses commenced in earnest in the late 1970s, a number of acetylene gas operated Dalen systems had been installed at offshore sites such as Auskerry, Start Point, Out Skerries etc in the early 1960s. At the time, solar power was available in an experimental form but was not regarded as the practical proposition, which it is today. As such, monitoring was installed and the lights were left with only an Observer. The first monitored light was by UHF radio from Fidra, where mains power was available, to Barns Ness, which was at that time still manned.

This was followed in the early 70’s by low-power dc installations of the three sites of Ushenish (to Neist Point), Dubh Artach (to Ruvaal and later Rinns of Islay) and Flannan Isles (to Butt of Lewis). These systems were manufactured by Aga (Pharos) using Cossor UHF radio equipment and operated for 3 minutes every 2 hours whilst the light was on; sending digital messages via tones. After these successes, another high power link was installed between Holy Island and Corsewall in 1977.

A new development for NLB at this time was the use of the public switched telephone network (PSTN) from Stoer Head to Butt of Lewis, and thence to St Abbs Head, which was used as the monitor centre. This was by “RADLE” which even at the time were curious devices using a standard eight-track tape. Alarm messages were recorded by a lady in Bracknell who had the virtue of being able to speak at a constant rate allowing her to generate evenly spaced verbal messages, which fitted neatly on the tape. Several such units were installed at Rattray Head, Esha Ness, Fair Isle North and Ruvaal. However, the relentless march of technology led to the introduction of the “RADAC” at Eilean Glas and a replacement at Rattray Head. A voice synthesiser replaced the woman eventually with a mid Atlantic accent speaking cryptic messages.

Meanwhile, more ambitious automations took place at Barra Head and Sule Skerry where radio beacons operated automatically with Aga/Cossor UHF links to Ardnamurchan and Strathy Point. In common with the earlier links, the displays at the base stations were indicator lamps showing offshore status.

In the 1960s and 1970s, computer technology was very expensive and its use limited to those that could afford to have expensive air conditioned computer facilities. For example, PSTN and modem links to regional satellite centres connected the branches of the major banks in Scotland to their Edinburgh Headquarters. The PC revolution opened up the use of this sophisticated technology to all users.

By the mid 1980s, the “RADLE” and “RADAC”, which in their day were a cost-effective system, were about to be consigned to the scrap heap. The driving force for this in NLB was the construction of the new lighthouse at North Rona commissioned in 1984, which would require an UHF link to Butt of Lewis. If anyone has ever wondered why Fair Isle South, Rinns of Islay, Butt of Lewis and Cape Wrath were amongst the last automated sites, it was due to their selection as regional monitor centres along with Kinnaird Head and St Abbs Head to be manned with lightkeepers. The sophistication of the technology quickly rendered this idea redundant with a common Headquarters Monitor Centre being the obvious choice. Delays in provision of equipment meant that a NLB designed and constructed single point to point system served North Rona for the first five years of its life, as a queue of sites developed for conversion. This equipment used tones transmitted via a Tait UHF radio and is remembered as extremely reliable.

Monitor Centre

Within a year of the Monitor Centre going into operation in 1987, more than 20 PSTN sites had been connected using the latest 20 Mb hard disc, 640Kb RAM 5Mhz Olivetti M24 PC operating under DOS 2.11. Connection to the PSTN was via an external modem unit operating at 1200 Bd, known as a DLC or CS 400 according to whether RS232 single point connection or RS485 multiple connection was used. Former lighthouse keepers were trained as Monitor Attendants to provide 24-hour coverage. The UHF radio links to offshore sites used PSTN connection from the Monitor Centre to automatic regional radio link stations, such as Turnberry for the Clyde rock stations. In addition, BT provided VHF radio telephone links, later replaced by microwave, to Ruvaal, Rinns of Islay and Inchkeith. NLB still pays a normal line subscription for these and they continue to operate as a normal telephone service.

Hard disc capacity has increased to 12.9 G Byte, RAM to 128Mb operating at 450Mhz with the new Realflex software, which has a specially written driver to interface with the old “Hermes” system. As a result of the complex protocols in use, the CS400s from the old system are still used for communicating by PSTN with existing outstations, while the Datac system uses conventional PSTN modems.

Other technology

A system called minisig was used to monitor Monach and Gasker lights, and originally to cover the Whale Rock buoy. In addition the Ardnamurchan experimental buoy used the same equipment installed by Trinity House Lighthouse Service Research & Development for experimental purposes. This is a narrow bandwidth very low power VHF system with relatively long range capability. It was not very versatile and was phased out as part of the overall monitor programme.

Over four decades NLB has continued to explore the available technology within the constraints of existing affordable technology and power available on each site. These experiments have included VHF Meteor Scatter systems, which bounce a signal off debris in the troposphere; satellite links using the Inmarsat marine communications system and HF radio