DVA - Snow safety

Whether you're a ski tourer or an off-piste skier, you'll need the basic safety equipment: shovel, probe and avalanche transceiver (Avalanche trans ceiver). The airbag is on the rise, and could soon become a basic piece of safety equipment too.

What is an avalanche transceiver?

• The principle

An avalanche trans ceiver is an electronic device worn on the body. In transmit mode, it emits sound signals (frequency 457mhz). In receive mode, it picks up these signals. When you're skiing, your dva is in transmit mode. If you find yourself buried under an avalanche, people in the area will switch their dva to receive mode to pick up the sound signals and locate you. All dva models on the market transmit and receive at the same frequency, and are therefore compatible with each other.

• Analog or digital?

Until 1998, manufacturers used analog technology. In this case, the signal from the transmitting avalanche transceiver is converted into sound waves by the receiver. When a receiving transceiver picks up a transmitting transceiver, it emits a "beep" which is louder the closer the two devices are to each other, or the more correctly they are oriented in relation to each other. A potentiometer can be used to vary the sound intensity of the signal, by adjusting the sensitivity of the receiver. All avalanche transceivers manufactured before 1998 were analog.

In 1998, a second generation of avalanche transceivers appeared, using digital technology either exclusively or in conjunction with analog technology. These are known as digital avalanche transceivers. The signal from the transmitter is analyzed by a microprocessor which converts it into two types of visual indication:
- a progress indication (numerical value appearing on a screen);
- a direction indication (diode or arrow which lights up when the receiving beacon is correctly oriented in relation to the transmitting device).

Is the analog D.V.A. now obsolete?

The answer is yes! And for several reasons!

Secondly, "current and future devices no longer take into account compatibility with analog avalanche transceivers (frequency tolerance, signal shape, etc.)", observes the FFCAM. Even if your analogue avalanche transceiver works perfectly, there's still a big risk that you won't be spotted under the snow by modern avalanche transceivers.

The third argument is the ease of use of digital avalanche transceiversis a decisive factor in panic situations. Even a trained rescuer (in the broadest sense of the term) is affected by a number of external factors, such as his or her relationship with the victim, or stress. Enough not to add an avalanche transceiver requiring a level of thinking worthy of a chess player in the finals of the world championships. Even if digital avalanche transceivers don't do the thinking for you, they're more intuitive to use.

Choosing the right avalanche transceiver

There's a wide choice of avalanche transceivers on the market, including the historic Arva brand, the mountaineering brand Mammut and Pieps for mountain safety products. Several manufacturers have entered the avalanche transceiver market, to the point where the skier doesn't know which to choose, between ease of use, richness of functions, or simply price.

• First criterion: ease of use and legibility.

This is the ultimate criterion for choosing a DVA, and concerns first-time buyers as well as the more experienced. As Anena points out, shape, size and weight are not criteria.

At the start of a hike, activation of the transmit mode should be a one-step operation and should not lead to confusion. When searching for a victim, switching to receive mode should be done instinctively, for example by pressing a visible button. The display must clearly indicate the direction of progress towards the victim, without any possible ambiguity.

The search bandwidth corresponds to twice the useful range, i.e. 70 m maximum: when the rescuer is in the middle of the flow, he will pick up a signal 35 m to the left, and 35 m to the right. So don't be fooled by a data sheet that says 60 m useful range - it's not possible. However, it should be noted that the longer the range, the less time the rescuer will spend searching for the first signal.

On the buried person's side, signal transmission power also depends on the quality of your avalanche transceiver; unlike the reception aspect, however, manufacturers don't give any figures, so it's difficult to compare the transmission power of different avalanche transceivers.

• Fourth criterion: Diversity of functions.

In addition to the basic capabilities listed above, all avalanche transceivers include functions to make searching easier, provided you know how to use them. The most obvious is marking: when the DVA picks up several signals, it automatically leads to the strongest one. Once the person has been located, it is possible to block the signal to search for another victim.

Some avalanche transceivers display the fact that they are picking up several transmitters. This information, essential for professionals, can be confusing for novices. The latest devices can also be used like a GPS, with a screen that schematically displays the steps to follow, from sweeping the avalanche zone to snail probing, or displaying a map with the estimated position of victims. Once again, it's essential to practice using them before you go skiing, so that you don't end up with too much information to manage at the crucial moment.

Maintaining your avalanche transceiver

An avalanche transceiver, like any electronic device, must be stored away from heat and in a dry place. At the end of the season, remember to remove the batteries, as manufacturers' warranties do not cover damage caused by leaking batteries. In addition, removing batteries at the end of the season allows you to think about putting in new ones for the new season.
Another useful recommendation: have your device checked by your manufacturer or in-store within 5 years of purchase, and then every two years. These overhauls enable manufacturers to recalibrate the antennas, as well as checking the condition of the casing, the battery switch, etc.