Banana Skins – May 2021 (#330-332)

330.  VCR/CD/DVC combo TV sends out false distress signals

This October, Chris van Rossman of Corvallis Oregon turned on his do-everything combo TV and got a big surprise—the police, the Civil Air Patrol, and the County Search and Rescue Officers knocked on his door. Apparently, Mr. van Rossman’s flat screen, VCR/CD/DVC combo TV had developed some sort of strong emission (a parasitic oscillation, more than likely) at 121.5 MHz, which is a rescue frequency used by aircraft and boat distress transponders and monitored by orbiting satellites. This service uses an uncoded analog carrier detection system, and is therefore rather sensitive to unauthorized transmissions. 

When the distress signal was picked up from the satellite, the information was picked up by the Air Force Coordination Center at Langley Air Force Base in Virginia. Langley in turn called the volunteer Civil Air Patrol in Oregon, which in turn contacted Benton Country Search and Rescue for help in locating the signal. Using radio direction finding equipment, the officers were able to narrow the source down to a few possible units in Mr. Rossman’s apartment building. When they knocked on his door and he turned off his set to answer, the signal disappeared.

David Mandrell, the CAP squad leader had heard of similar inadvertent interference from consumer equipment, but often it was weak enough to be ignored. This particular instance of interference was unusual because it was abnormally strong. Mr. Rossman was simply warned to keep his TV turned off or face fines of potentially up to $10,000 per day for emitting a false distress signal. He has contacted the set’s manufacturer, whose technicians had never heard of a case like this, and has agreed to send him a free replacement. 

(Taken from Conformity magazine, Jan 21 2005, “TV Interference Triggers Aircraft Rescue Satellite Response”, and published in the Corvallis Gazette-Times, Oct. 17, 2004) 

331.  Illegal truck radio transmitters suspected of causing two bus accidents

It has been reported widely in the Japanese press that electromagnetic interference caused by illegally modified transceivers on trucks is suspected of causing two accidents by disabling the braking system of commuter buses. Mitsubishi Fuso Truck & Bus Corporation announced that two models of its buses are adversely affected by high-powered EMI from short distance and its braking system may not function properly under such conditions. Specifically, its braking system that detects the wheel-locking condition falsely triggers due to the EMI and thus the brake doesn’t work as intended.

Two accidents were reported last year where the bus drivers reported that the brakes suddenly stopped working. However, after the police investigation, no visible malfunction was found. The manufacturer continued investigation and found that high-powered radio signals emitted by a nearby transceiver (illegally modified and thus 1,000-10,000 as strong as permitted by law for such transceivers) can interfere with its braking control unit, resulting in false information that the wheels locked due to braking.  Upon this false information, it seems (my interpretation from what I read various reports) that the control unit decided to release the brakes, and thus caused unintended loss of braking.

It is not known whether such illegally modified transceivers were present nearby in two accident cases.  But in other two instances where loss of braking was observed, the bus drivers saw suspicious trucks nearby. The company could reproduce the condition in live experiments, and it will refit the 2200+ cars by replacing the control unit, sensors, pipes, circuit harness, etc.  I think the company should be commended for its continued investigation after the accidents.

(An extract from the Risks Digest 5 Jan 04 issue that is posted at: http://catless.ncl.ac.uk/Risks/23.09.html. Sent in by Simon Brown of the HSE, January 2003. The Risks Digest describes itself as a “Forum on Risks to the Public in Computers and Related Systems”, current issues can be read at: http://www.csl.sri.com/users/risko/risks.txt.)

332. Concerns about worsening interference in medical and healthcare discussed

Is there enough regulation in the EU to avoid the potentially fatal outcomes for patients that could occur when electromedical or electronic medical devices interfere with each other or with other equipment? And are manufacturers taking enough care to ensure that they are not exposing themselves to the litigious consequences of being negligent in ensuring that such devices operate properly in the environment for which they are intended?

Those were the questions being asked on June 15 in London at the Management Forum Regulatory Update for Electromedical Device and Equipment Manufacturers in London. While actual cases of serious incidents and deaths caused by such interference are difficult to establish given the anecdotal nature of many reports, a UK study dating back to 1993, suggested there had been 23 serious incidents and two fatalities due to electromagnetic interference that year.

Unfortunately, more recent events are “hard to nail down” one regulator told the meeting, although “we know there are causes and effects, and with basic proximity testing you can prove this”. Hospitals are generally reluctant to report incidents, delegates at the meeting heard, because of the fear of blame, as was the case when one surgeon answered his mobile phone in the operating theatre, causing the anaesthesia machine to reset.

Without doubt, potential interference is a growing problem and, unless something is done to keep up with the rapidly changing technological environment, manufacturers are going to find themselves increasingly at risk of being accused of lack of due diligence and even negligence.

Consultant Trevor Lewis of Medical Device Consultancy told the meeting: “We know that there is a lot [of interference] going on. Whether it is being reported is another matter. To get more people to report we should avoid apportioning blame and that may move forward the trend to report.”

Mr Lewis is adamant that something needs to be done and quickly on an EU level. “I’ve seen this trend [of electromagnetic interference] moving forward, and I want to be able to advise my clients accordingly to make sure that they are robust from a regulatory and liability point of view,” he said.

This not an issue that manufacturers can solve on their own, he insisted, since about 85% of companies operating in this area are small firms and simply cannot afford the resources to analyse the environments in hospitals into which their equipment is placed. Instead, Mr Lewis believes “it would be good if the regulators could characterise safe environments – not only in hospitals, but in homes as well”.

To what extent the hospital managers are also responsible for ensuring that electromedical and electronic medical equipment is used in situations where the risk of interference is avoided, seemed unclear at the meeting.

“Very few NHS hospitals are taking this seriously,” Chris Marshman, managing director of York EMC Services and chairman of the conference said. Most hospitals, he continued, have medical physics departments that would be capable of the necessary assessments yet it “seems nothing is happening and there is no co-ordination”.

It is not only the decisions about where to install products that need to be taken by those in hospitals with a full understanding of the potential interference problem, it is also decisions concerning the management of the maintenance of equipment. Some clinical engineers working on equipment in accident and emergency, for example, may be unaware that if they remove the screws from an item of equipment during maintenance and then fail to put them all back, that this could change the EMC of the equipment and potentially increase risks.

So with all the risks bound up in the use of electromedical and electronic equipment, what can manufacturers do to ensure to prove that they have taken all reasonable steps in terms of addressing issues that arise through a constant risk analysis and management to avoid the risk of interference?

The key here for manufacturers is to ensure instructions for use are clear and readily available, to provide a good installation guide to ensure that the user can safety install the equipment and to use historic good practice to give indications about the careful “zoning” of equipment in the intended environment to avoid interference problems, Mr Marshman said. Also necessary is any further information that will ensure the device is EMC compliant throughout its lifetime, including flagging up in the maintenance file any essential steps, such as putting back all the screws on equipment and explaining why.

“Care is needed on both sides,” Mr Marshman insisted. “The manufacturer with the instructions, and users to make sure that they know what they are doing…The duty on users is to make sure that they are doing the best they can.”

Finally, a word of warning was given by Ian Cutler, senior medical devices expert and European regulatory affairs consultant to the medical devices industry. Mr Cutler reminded delegates that the healthcare environment is becoming increasingly litigious and asked the meeting to imagine what a prosecuting lawyer would ask, should an incident lead to court action. “Did you consider how X could have had an effect on your product? And, did you have enough technical data to justify your claims on performance?” would be among the likely questions and companies would be found to be totally negligent to ignore potential new sources of interference.

So, it is clear that companies operating in this sector expose themselves to being prosecution unless they are constantly updating their knowledge of potential and changing risks and applying it to products being marketed and in the field. Unless manufacturers perform constant post-market surveillance and risk management and act immediately on their findings, they could face sanctions, including criminal prosecution. 

(Taken from “Is the EU underplaying the device interference problem?”, Clinica – World Medical Device & Diagnostic News: Issue 1113, p8 , filed 21 June 2004. Trevor Lewis can be contacted at: lewlink@btclick.com) 

About The Author

Keith Armstrong

After working as an electronic designer, then project manager and design department manager, Keith started Cherry Clough Consultants in 1990 to help companies reduce financial risks and project timescales through the use of proven good EMC engineering practices. Over the last 20 years, Keith has presented many papers, demonstrations, and training courses on good EMC engineering techniques and on EMC for Functional Safety, worldwide, and also written very many articles on these topics. He chairs the IET’s Working Group on EMC for Functional Safety, and is the UK Government’s appointed expert to the IEC committees working on 61000-1-2 (EMC & Functional Safety), 60601-1-2 (EMC for Medical Devices), and 61000-6-7 (Generic standard on EMC & Functional Safety).

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