(cover photo by I. Hudakov)
What follows is not a user manual nor a tutorial on how to carry out a self-rescue in an avalanche. For these topics, it is advisable to consult a specific technical manual and the manufacturer’s instructions, and also attend a course of theoretical instruction and training on field.
A lot has been said and written about avalanche beacons, but perhaps there is no synthetic picture of the features and functions which are truly important to know, and common to all models on the market. From the experience of more than 30 years on the snow, of our staff and professional partners, here below are the 15 key points to look after for optimum utilization of avalanche beacons and safety.
#1 APPLICABLE STANDARDS
The avalanche beacon devices In Europe and internationally must comply with EN 300718 standards, which require specific technical characteristics in terms of emission signal (see below), field strength, reception sensitivity, spurious emissions, and resistance to shocks, water, temperatures.
# 2 TRANSMISSION SIGNAL
According to the EN 300718 standards, each device must operate according to the following parameters: –
a) pulse period of 1000 ms (1 second) with tolerance of +/- 300 ms, therefore in the range 700 – 1300 ms;
b) pulse duration> 70 ms;
c) non-pulse duration> 400 ms.
To better understand the above, see the graph of the typical emission of the transceiver signal in the figure. In high quality devices, the period is close to the maximum of the range (say, at least 1100 ms) and the pulse duration equal to or slightly higher than the minimum of the standard (say 70-90 ms). This will make it easier for any other device in reception (search mode) to distinguish the signals from different devices located in the same search area (multi-burial situation), especially when this is restricted.
Note : some top range beacons have the “Pro-check” function, which allows you to detect the aforementioned parameters (frequency, period, pulse duration) of another device in transmission mode. Alternatively, for professional use there are portable testers available.
#3 ANALOGUE OR DIGITAL DEVICE ?
It is definitely recommended to use a modern digital device with 3 antennas. The old analog devices, perhaps with only 1 or antennas, are no longer acceptable according to current safety criteria, because:
1) the signal quality (see # 2 above) is poor and sometimes even out of the range prescribed by the standards;
2) the “poor quality” signal coming from an old analogue transceiver disturbs the search of other devices in the area, especially, in case of multiple burials;
3) the search in cases of deep burial is far more problematic with an old analogue transceiver.
Most transceivers use alkaline or lithium batteries. The latter are definetely better, both in terms of duration and efficiency in cold conditions. Absolutely to be avoided the rechargeable batteries.
Almost all devices ask you to set the type of batteries (alkaline or lithium), at each replacement, in order to optimize their use and duration The state of charge is generally shown on the display while switching on.
According to the model, it is necessary to have a residual charge of at least 30-50% (keep in mind that the highest consumption takes place while receiving in the research phase).
The EN 300718 standards require, for new batteries, a minimum duration in emission of 200 h at + 10 ° C followed by 1 h in transmission at -10 ° C.
Beware: some devices require a reset each time the batteries are removed and replaced; it is recommended to strictly follow the manufacturer’s instructions. Among other things, it is recommended to replace all the batteries with new batteries of the same type.
#5 GROUP CHECK
Most transceivers have a specific function for group cross-check of the devices, in transmission and reception, which must be performed before leaving for the excursion.
#6 SEARCH PHASES
The modern digital beacons have a display where the research phases are guided by a “user friendly” symbology. Optionally they also offer an acoustic signal, similar to that of the old analogue devices.
The most important feature is the ability to immediately identify and show on the display the number of signals being received.
Only some top end devices have the ability to switch from digital to analogue search. This need arises when, in case of multiple burials within a small area, the digital processor has difficulty in separating the signals. However, analog research is quite different and requires special training (this is beyond the scope of this article).
However, with digital beacons, to facilitate the separation of the transmitting signals, is sometimes sufficient to stop the search for about ten seconds, and wait for the processor to reset and resume its status.
All transceivers have this essential function whereby, once the buried subject is found, the relative signal is “marked” ( = excluded from the subsequent search).
#8 AUTOMATIC SWITCH TO TRANSMISSION MODE
Almost all transceiver models have this (optional) function whereby, when in search mode (receiving), after a period of non-mobility of the device, it automatically switches to transmission mode. The period of non mobility can be set (the suggested standard is 4 min.). This is an extra safety feature for avalanche rescuers if they happen to be buried by a second avalanche.
Some recent models have an intelligent use of the antennas that allows, for example, to activate in a differentiated way and selectively one or more of the three antennas in transmission and / or reception.
#10 VITAL FUNCTIONS DETECTION
Some top-end devices allow to choose whether to activate the sending of a buried persons’s vital functions. What does it mean ? A motion detector is inserted into the transceiver and sends the motion signal to a receiving device. This makes it possible to establish a priority in search: the devices that do not transmit signals of motion are those of the victims with the highest probability of being (regretfully) already deceased.
Warning: when activating this function is also necessary to pre-set the region of the world where you are located, since different regions utilize conventionally different transmission frequencies of this signal. Some countries do not allow to utilize any specific radio ferquency for this purpose. In any case we recommend to read the manufacturer’s specifications carefully.
#11 EXTRA USEFUL FEATURES
Among the various extra features, we outline the following:
a) Some devices are provided with a USB and/or bluethooth connection for settings and firmware updates.
b) The availability, on some models, of an integrated Recco reflector is interesting and useful.
c) Night use: in case of searching in the dark, it is essential to have the function (even automatic) of the display backlight.
d) Voice Guidance: Ortovox has been the first beacon manufacturer to introduce this special feature in the Diract models. No doubt the voice guidance may represent a futher help while searching, although it is not meant to replace the indications of the display.
However be careful with the less useful extra features that could reduce battery life.
#12 HANDINESS OF USE
If you need to buy a new beacon , check that its use is comfortable and ergonomic even when wearing gloves.
Cell phones and other electronic devices can disturb the reception of the transceiver signal. All beacon manufacturers recommend turning off cell phones nearby.
The device’s firmware shall always be updated. It is usually possible to carry out the update to the latest release at your reseller, or by connecting the device to an already updated device. In any case, it is recommended to have the device periodically checked by an authorized service centre (every 3 years or according to the manufacturer’s instructions)
We have always stressed the importance of knowing your device thoroughly and perform frequent training sessions, both in artificial test fields (such as the one active at Plose) and on the snow.
We quote from the web site of the American Avalanche Association : “Beacons only work if you practice regularly with them and most people don’t practice enough. As a result, beacon use has not increased survivability rates as much as one would hope. For people who practice regularly, however, beacons have saved many lives and they work very well.”