Monitoring

The Board has put in place a policy to monitor all its active land and sea based Aids to Navigation at its Monitor Centre in Edinburgh. The estate has 360 such Aids to Navigation of which more than 160 are at present monitored and one buoy using AIS. To implement the extension of and updating of the existing monitoring system, a project was started in 1999 this will continue on a rolling basis until 2010.
On completion of this project the correct functioning of all active Aids to Navigation i.e all those that transmit as part of their function, whether it be light, sound or radio signal, will be monitored from Edinburgh giving improved system reliability and availability.

Monitoring Scottish Lighthouses
by Roddy MacKay,
Capital Projects Engineer

(Article from the Northern Lighthouse Board Journal Christmas 2001)
Monitoring - In the Beginning …
The monitoring of lighthouses is not new, amongst the early methods the Northern Lighthouse Board (NLB) used a signal tower at Arbroath to communicate with the keepers at the Bell Rock Lighthouse. When the smaller unmanned lights were installed at the end of the nineteenth century, an Attendant or Observer was appointed by the Board to confirm correct operation. This situation persisted until the "electronic" age when NLB's first attempt at monitoring and remote control was undertaken by the Radio Department at Inchcolm fog signal in the Firth of Forth. The lightkeepers at Inchkeith operated the fog signal and a VHF radio link allowed them to turn on and off the fog signal and generators. Their operation was monitored using a microphone and an open VHF channel back to Inchkeith. Diesel generators were used to charge the fog signal and monitor system batteries - this system operated from the late 1960s until 1974.

Automation
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 3 'hardship' West Coast 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. The woman was replaced eventually by a voice synthesiser 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 and some technical stuff
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.

Y2k - The Beating the Millennium Bug
The Monitor Centre and the system operated relatively undisturbed for more than a decade with around 72 connected stations, with only the occasional PC upgrade, until the millennium bug appeared on the horizon. Indicator lamps had been replaced with textual displays on a VDU with printers and data storage producing a complete system log.
"Hermes" software had reached the end of its life span and its scheduled replacement was accelerated to be in service before the 31st December 1999. This was achieved with a few weeks to spare after tendering for the supply of a completely new system which would remove the software bug. Phased replacement of the existing system together with the inclusion of the newly solarised and renovated former Dalen stations such as Auskerry and Start Point referred to above was also included as part of the project. In an effort to improve the integrity of the service offered by NLB, it was simultaneously decided to monitor all previously unmonitored Aids to Navigation (AtoNs) including all buoys and minor lights. An extension of the system from around 80 locations to over 350 was thus envisaged.
Y2k problems were not limited to the Monitor Centre as the radio link stations used a single board PC for system control at each RLS site. A suitable replacement was identified and all ten sites were replaced well ahead of schedule.
The expanded system is possible due to further technological advances, reliable use of solar power, more efficient electronic systems, digital synthesised UHF radios and cellular phone networks have contributed to this. The use of sophisticated software to allow networking and multiple path connections to many sites reduces the need for high power long-range radio links.
Datac of Dublin (also suppliers to Commissioners of Irish Lights) secured the contract and the first replacement of old equipment took place at Rubh Re where the PSTN equipment monitoring that site was replaced as a result of providing a radio link site for monitoring of the newly modernised Rona lighthouse. Communication can be by UHF or by a roaming GSM service at either site.

More technical stuff
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 new Datac system uses conventional PSTN modems. A major improvement of the new system is that the station data can be transmitted around the corporate computer network using a modem link and this will be available during the next few months.

The future
The expanded system for buoys and minor lights will be developed in the next 12 months and the Operations Department has already identified several buoys in the Oban area for inclusion in the monitor system. This fits in neatly with the solarisation and monitoring programme for minor lights as a number in the Sound of Mull and Loch Linnhe are about to be converted. These are necessary to provide a fixed network infrastructure for the floating AtoNs.
As Oban Depot nears being fully operational the backup Monitor Centre equipment can now be set up in the small tower above the old store. In addition, it is intended that the monitor information will be more available around the office.

Other points of interest...
DGPS site plant information is covered on NLB monitor system but as the DGPS equipment is a fully integrated system and allows comprehensive remote control, the DGPS system is independently monitored using PSTN lines with a PC based display at NLB fully integrated via the internet with the other GLAs' control centres. Additionally, Ordnance Survey purchase raw GPS data via an on site ISDN modem and retransmit this as part of the their Internet based "Active Network".
There is a system called minisig used to monitor Monach and Gasker lights, and originally to cover the Whale Rock buoy. In addition the Ardnamurchan experimental buoy uses 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 is not very versatile and will be phased out as part of the overall monitor programme.
The replacement system is capable of using all communication media including satellite, which is still not cost effective although it could prove to be the only practical way to monitor a number of sites.
Over the last 3+ 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.

Somewhere in the future ...
At present the Radio Communications Agency are investigating the use of the UHF radio bands and as a result of this further emphasis may have to be placed on the use of satellite networks or more GSM than intended, or alternatively moving to higher frequency bands which would cause problems for longer length links.