A first-of-its-kind cave rescue exercise in Romania took place this week in the karst area of the Apuseni Mountains, carried out by French and Romanian speleologists, the Cluj County Council (CJ Cluj) announced.

“The close collaboration between Cluj speleologists and the French team from Speleo Secours Isere has continued uninterrupted for several decades. A team of French speleologists from Speleo Secours Isere is currently in Cluj, in the karst area of the Apuseni Mountains. The French team, together with members of the Cluj County Public Salvamont-Salvaspeo Service, a county-level public institution subordinated to the Cluj County Council, as well as speleologists from Bihor and Hunedoara, carried out a first exercise for cave rescue in Romania in Humpleu Cave. The wireless through-the-rock communication system was thus tested, enabling rescuers outside the cave to communicate with those inside, without the need to lay kilometres of cable, as is the case with traditional cave telephony,” the CJ Cluj said in a release.

According to the source, the French system does not require cables but uses the principle of transmitting injected current through the rock and variations in the Earth’s magnetic field, which in turn induce electric currents. Thus, between terminals located outside and inside the cave, or at two different points inside the cave, once currents have been injected into the ground via electrodes, voice messages can be transmitted. The initial system, called “Nicola” is now in its second generation – “Pimprenelle”, and the French team is already working on its third generation. The main advantage is the ease and speed of implementation. The main disadvantage lies in the influence of morphological factors of the rock layers such as discontinuities and non-conductivity, as well as atmospheric factors including storms and atmospheric ionisation. For this reason, multiple tests are required in order to determine the appropriate positioning of the electrodes that inject current into the ground, depending on the characteristics of each cave.

“Through such joint training activities and the practice of new communication techniques, Cluj speleologists are preparing to manage efficiently the emergency situations that may arise in the underground environment,” Cluj County Council President Alin Tise is quoted in the press release as saying.