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Frequency Precision

Reducing Risk with Sensor Technology

Frequency Precision is a company dedicated to applying technical and engineering skills to helping people who may be dependent on others. They have developed a range of sensitive but durable sensors which can help alert carers if someone puts themselves into a potentially dangerous situation.

The story of Frequency Precision started is a personal one: Doug Dwyer’s mother was living in a nursing home and he wanted her to be able call for assistance. However, as an engineer and inventor, he took matters into his own hands and, working in a shed in Devon, he created a pager system for her use.

Subsequently, his mother developed dementia and wasn't aware of the risks of getting up out of bed without assistance. Again, Doug came up with a solution: an air pressure sensor that would go under the mattress. The design was so discreet that his mother didn't notice it but would give her carers early warning if she attempted to get out of bed.

The success of his inventions led to the formation of the company: Frequency Precision.



Introduction to Sensors and Alerts

What is the alert system?

In simple terms this technology depends on 3 functional elements:

  1. A triggering (activating) element, which may be a sensor or a push button alert. This is with the person being monitored
  2. A transmission system (to send a signal between the triggering device and the alert device): Frequency Precision uses WIRELESS technology (or, alternatively, the sensor can be connected directly into an existing call system).
  3. An alert component, which might be a simple bleeper, a pager or a more sophisticated monitoring system. This will be used by the person who is doing the monitoring.

Sometimes more than one function is combined in a single device.


Users: Activators (the monitored person)

Two groups of people may benefit from activating an alert system:

  1. People who are physically weak or frail but whose mental abilities are likely to be normal (cognitively intact). People in this group might benefit from a Call-Button alert or a Fall Alert device.
  2. People may be confused (cognitively impaired) due to conditions such as dementia and require sensors to alert their carers if they might be putting themselves in danger, for instance by leaving their room. People in this group may be quite physically active.


Users: Supervisors (the monitoring person) 

There are, most commonly, two types of monitoring person in two corresponding situations:

  1. Domestic - Sensor-Alert systems can be used at the person's home in a domestic environment to help partners or other family and friends keep the user safe. A simpler set-up will often be enough in this situation.
  2. Professional - Sensor-Alert systems may also be helpful in residential and nursing homes as well as hospitals. In these cases, multiple people may need to be monitored and a more complicated set-up may be required.

 A set-up needs to be designed according to the needs of the person being monitored and those of the person(s) who are doing the monitoring.


Sensor Types



Standard Bed or Chair Pressure Mats

These air pressure mats use highly sensitive, patented ‘Airlert technology based on the same principles as the original mat developed by Doug Dwyer.

A rubber tube connects the pressure mat to a sensor box, powered by 2 x AA batteries which can last up to two years without needing to be changed. By measuring changes in air pressure, the system reduces false alarms and unlike some other products mats can be placed discreetly and comfortably under mattresses or cushions. The Bed Pressure Mats will work with Airflow Pressure Relieving mattresses and with profiling beds - considered difficult for traditional sensors.

This technology is now used by thousands of people in private homes, care homes and hospitals around the country. It is said to be by far the most reliable and easy to use sensor on the market.

Scroll down to the bottom of the page to learn more about ‘Airlert technology.


Bed Occupancy Mats

While standard bed or chair mats send an alert as soon as the person gets out of bed, the bed occupancy sensor sends an alert if a person doesn’t return to bed within a defined period.

The standard bed or chair mats would be used when there is someone nearby to receive the alert and act on it – e.g. in a hospital or nursing home, or if somebody in their own home wants to know as soon as the monitored person gets out of bed. They require somebody to act on the alert immediately – e.g. check if the person is OK or if they need help getting to the toilet etc.

In contrast, the bed occupancy sensor might be used if there is nobody in the same property, e.g. an elderly person living alone. In this situation, it would be more helpful to know if they got out of bed, but then didn’t return to bed within a defined period – because that could indicate that they may have fallen or may have wandered away into a dangerous situation.

Floor Pressure Mats

Frequency Precision floor pressure mat sensors reliably detect someone treading onto the mat. Appropriately placed, they will give warning the moment the person steps out of bed or through a doorway.

Although not based on Airlert technology these floor pressure mats are extremely durable and come with an anti-slip base. They can also be ordered with an optional machine washable ‘barrier mat’ to provide additional protection to the pressure mat and reduce trip hazards. 


Airlert Chair Pad
Airlert Chair Pad

Airlert Bed Pad (in place)
Airlert Bed Pad (in place)

Floor Pressure Mat



Infrared Motion Sensor

Sensor Eye with 2 'eyelids'


The PIR (Passive Infrared Motion) Sensor is a small battery-powered sensor that can be positioned to detect whether movement occurs in a specific area. It uses the same infrared technology as the systems used to turn on outdoor lighting and will work in both darkness and light.

The sensor is set up in position pointing towards the area where motion detection is required. In addition, the ‘eye’ of the sensor has two eyelids which move to direct the angle of the detection beam. They can be rotated to give a very tight angle or opened up to give a very wide detection field. By choosing the right location (for the sensor box) and setting (for the angle for the beam), the motion detection area can be set-up to suit most needs - for instance to detect movement:

  • in a bedroom indicating someone leaving their bed.
  • through a doorway.
  • in a corridor.
  • a particular area of the home that presents a risk to someone with dementia.

When a person walks in front of the sensor, a caregiver will receive an alert from anywhere in the home using the bleeper pager. Features of the system:

  • one-year battery life.
  • 400m range.
  • impact resistant plastic casing supplied.
  • 30-second timer starts after activation, allowing the carer to exit room.
  • each motion sensor can be programmed to display a unique message on the text pager, e.g. "room 1".
  • the motion sensor contains an accessory socket for a wired call bell or floor pressure mat.
  • any number of motions sensors can be linked to one or more text pagers.


Call Buttons
For the user, these are simply devices which can be pressed to alert someone else. Most commonly these will be used by someone who is cognitively intact. For the benefit of professional supervisors, many call buttons can be linked to a single pager and are compatible with all nurse call systems. The call buttons can take several forms.

Simple Wireless Call Button – at its simplest this can consist of a button which is connected wirelessly to an alert device, such as:

  • a bleeper to sound an alert that the user needs assistance within a range of 200m (can be extended).
  • a text pager with a customised message.
  • a mobile phone.

The call button can be worn as a pendant using a lanyard or can be worn with a wrist strap. The Call Button is supplied with a water-resistant case.

Easy Press Call Button - this works on the same principle as an ‘simple’ call button, but consists of a highly sensitive and easy to push pressure pad which can be activated by the lightest of taps from a hand, head or foot. These are particularly suitable for use by those with limited functional movement and can be placed anywhere, even in the bath.

Fixed (for instance to a wall) - the wireless fixed call button is battery operated and can be attached to a wall, door or surface with a range of 400m (which can be extended). Combined with a bleeper pager this is ideal for those hard of hearing. They can carry the pager around the house, and it will flash and vibrate if someone presses the button.
This can be used as a doorbell; the only snag is that the buttons aren’t waterproof, so they are fine in a porch but not totally exposed to the elements.

Fall Alerts
The Frequency Precision ‘Fall Alarm with Advanced Fall Detection’ provides added protection for those at risk, by alerting carers if a fall is detected.

The fall alarm works in the same way as a pendant Call Button alarm; however, it is worn like a wrist-watch and has extra features. An alert can be sent at any time, however, in addition the ‘Advanced Fall Detection’ technology will automatically alert carers or relatives to a fall. The alarm is waterproof and can be used in the bath or shower.

Carers can choose to receive alerts via a bleeper or pager which will work at up to 200m and are ideal for the home and garden. Alternatively, a mains-powered base unit can connect to a WiFi network and send messages over the Internet to a free mobile phone app.

To prevent falls from occurring in the first place, other sensors can be used to alert carers that a person is on the move and requires assistance.

Epilepsy:  Convulsion Sensors
Using Airlert technology, Frequency Precision’s Convulsion Sensors are accurate, easy to use and reliable. The system is designed to sense movement typical of a tonic-clonic epileptic seizures, in which the entire body shakes. The sensors are pressure-sensitive and can be adjusted for use in both adults and children.

A full-sized (198cm x 63cm) bed sensor mat is positioned underneath the mattress. There's nothing inside the sensor mat except for a thick layer of foam, which has many tiny air pockets within it, so the mat is discrete, comfortable and durable. Additionally, the simple structure means there is little inside to go wrong, making the mats:

  • reliable.
  • durable.
  • water resistant.
  • adaptable (so they work with all beds and mattresses - including hospital profiling beds and pressure-relieving mattresses).

The mat connects to a small control box which detects excessive movements typical of an epileptic seizure. The control box has a small dial to adjust the sensitivity, minimising false alarms. It is powered by two household AA batteries which will last for up to one year. When an epileptic seizure is detected, a message is sent to a pager (range 400m).

Door Sensors
This set comes complete with a linked wireless door sensor and easy to use pager, designed to prevent wandering of those with dementia or learning disabilities. Discrete, wireless door sensors will alert carers when a door or window is opened.

The compact door sensor is supplied with double-sided adhesive sticky pads, for easy installation and runs for several months on one battery. The sensor contains a useful sliding switch to turn it on and off.

Each door sensor can be programmed with your required message ("front door open", "flat 1" etc) which will be displayed on the text pager when the door is opened. An unlimited number of door sensors can be linked wirelessly to one or more text pagers, (range of up to 400m – which can be extended by adding a wireless range extender).


Call Button
Pendant Call Button

Falls Watch
Falls Watch

Easy Press Call Button


Alerting Devices

If a sensor is activated the carer who is monitoring needs to be made aware. There are several options with varying degrees of cost and complexity

These just make a noise and are cost-effective and simple to use but have limited functionality. 

Any number of Sensors or Call Buttons can be linked to one or more text pagers (and each sensor can be programmed to send a unique message). 

The Logger - A digital monitoring solution  (IN DEVELOPMENT – COMING SOON
The Logger is a small tablet which connects directly to your WiFi network and can receive signals from a variety of sensors (including: Bed-leaving & Occupancy, Chair-leaving, Convulsion, Door-opening, Motion, Door-bells and Call buttons).

The logger will allow a data from the sensors to be viewed more easily, to give a detailed picture of the activity within a home:

  • a record of sensor activity.
  • low battery alerts.
  • nurse response times.
  • multiple sites can be monitored from the same account.

Wireless Interface for Call Systems
A wireless receiver can be plugged into an existing nurse call point. Compatible systems include:

  • Medicare
  • Courtney-Thorne
  • Aidcall
  • C-Tec
  • Intercall
  • Quantec






Which System to Choose

The different products listed above can be combined in different configurations to suit particular needs. A few scenarios have been listed below, but we would advise contacting us to discuss your needs whether ‘At Home - For Domestic Carers’ or for a complex multi-user system for a nursing home or hospital.

"My carer lives in the same house as me":

  • A call button or sensor linked to a pager will alert a carer within the range of an average home and garden.
  • A pager is carried by the carer.
  • Quickest response time - the carer is alerted immediately.
  • Low cost - just a one-off payment to buy the equipment. No subscription needed.


"I need to be able to alert my family who lives nearby":

  • A call button or sensor linked to our base station uses your WiFi signal to send a message to a mobile phone.
  • The carer doesn't need to be in the same house.
  • Medium cost - just a one-off payment to buy the equipment. Unlimited messages are included within the cost price.
  • Medium response time - the carer is alerted by receiving a message on their mobile phone.
  • You can add a base station to any of our wireless call buttons or sensors.


"I need somebody else to contact my carer or call an ambulance when I need help":

  • A 24/7 call centre monitor or dialler will notify call centre staff who will alert emergency services.
  • We supply sensors compatible with all monitors/diallers.
  • The monitor/dialler would need to be purchased and installed separately.



"The nursing staff decide which equipment the residents require. If the resident is prone to falling out of their chair they’ll be given a chair mat. If they just want to know if when the get up in the night, or if they are a risk of falling out of bed, they will be given a bed sensor. We also use the floor mats in a lot of different ways. If you put it in front of the bathroom door it will alert you to them using the bathroom, positioned next to the bedroom door it will alert the staff to someone leaving their room."
Andy Dunn, Maintenance Technician - Augustinian Care



Q. Do I need to pay VAT?

A. If you have a long-term medical condition you do not need to pay VAT on most products that we sell. We can advise you this and help you with the simple paperwork.

Q. My Airlert Mat has stopped working, What should I do?

A. This system is generally extemely reliable, but if you have a problem start by checking that the rubber tubing between the mat and the sensor box is connected. If there is still a problem, try changing the battery in the sensor box and pager. You can always call us at Fortuna Mobility for further advice.

Q. Are the sensors easy to set up?

A. The sensors and pagers are supplied ready to use straight out of the box. All batteries are included. 

Q. Will your sensor alert the emergency services if I fall?

A. No, our sensors are designed to alert a carer within the same property that you need help. They can also be linked to a mobile phone to alert a family member. 

Q. What is the wireless range between the sensor and the pager?

A. The wireless range is generally about 200 meters, meaning that the pager can be carried by a carer around the home including in the garden. 

Q. If I go to the shops, can I carry the pendant or falls watch with me so that I can get help if I fall?

A. The pendant and falls watch will only work when you are at home or in the garden. This is because they have to be within range of the pager. 

Q. Can I have more than one pager to go with my sensor?

A. As many pagers as needed can be linked to one or more sensors. 

Q. Can I have more than one sensor to go with my pager?

A. As many sensors as needed can be linked to one pager. 


Airlert Technology

A unique air-sensitive system to provide safe and reliable monitoring of those in care. 

Air pressure mats are highly sensitive and detect the change in pressure as a patient gets out of a chair or bed. Frequency Precision uses patented Airlert technology invented by company founder Doug Dwyer.

A traditional 'contact' type pressure mat consists of two pieces of foil separated by a layer of foam. When a person steps onto the mat, the two pieces of foil touch each other through the holes in the foam, triggering the sensor. If used in a bed or chair, when a person gets up, the opposite happens - the two pieces of foil lose contact, also triggering the sensor.

Unfortunately, there are several limitations with this traditional design:

  • The foam layer tends to degrade and flatten over time, causing the two pieces of foil to touch even when there is no pressure on the mat. This means that this type of pressure mat has a limited lifespan before it stops working properly and many tradtional mats come with an 'Expiry Date' marked on them.
  • There are electrical connections inside the mat itself, which can be damaged through heavy use leading to false alarms.
  • To reduce the risk of damaging the foam and electrical connections, this type of mat generally has to be stored flat.

The Airlert technology used by Frequency Precision represents a major improvement over traditional designs. An Airlert pressure mat is based on the same principle as a self-inflating camping mat: it contains nothing except for a thick layer of foam, which has many tiny air pockets within it. The foam is covered in a durable, flame retardant airtight cover. A rubber tube connects the pressure mat to a sensor box, powered by 2 x AA batteries which can last around a year without needing to be changed. The design is simple and reliable as there are no electronics or wires inside the mat.

The foam is naturally self-inflating so when pressure is removed it will expand to resume its original shape. This sucks in air which is measured by the control box and if a certain pattern of pressure (such as occurs if a person gets out of the bed or chair) is detected, the sensor will create an alert.

Advantages of Airlert Technology.

The mats:

  • contain nothing but foam and with no electronics inside there is less to go wrong, making them extremely durable and long lasting.
  • are water resistant.
  • can be rolled up or folded without reducing reliability.
  • are positioned under the mattress and are comfortable and discreet
  • will work beneath air flow mattresses and on profiling beds.
  • are ‘full-length’, so that the whole area of the bed is covered by the sensor. This reduces the risk that the user is on the bed but not on the sensor which means that the sensor will work more effectively.
  • detect subtle variations in pressure change and only alarms when a certain level of pressure has been reached. Patients can roll around on the bed or chair without false alarms.
  • have no electronics inside them, so there is less to malfunction, reducing the risk of false alarms.
  • rapidly transmit a fall in air pressure to the sensor box, so the system is fast to react as the person begins to get up.  
  • The sensor box can be supplied as 'normally open', 'normally closed', or 'change over' meaning it is compatible with any nursecall or remote monitoring dialler. It is also available as a stand-alone wireless pager system.
  • Although the default settings will work well for the vast majority of users, the sensitivity of the Airlert sensor can be adjusted to suit any individual using it, unlike a traditional system - for example, according to their pattern of  movement or for use with a person of very low body weight.






Chair mat with rubber tubing





Sensor Box

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