poland


yellow during the fi rst weeks while the system was being commissioned. In the telephone exchange, Wojciech Rabczuk pulls


from an equipment rack a folding terminal screen with keyboard. “It’s very simple here to manage the system”, he says. “We are connected to this node. It’s the same as you have seen before. You can see one, two, three, four, fi ve stations.” T e fi fth station, he explains, is the PC node to which we are connected, right beside us. At one of the sites, only a single TETRA carrier is installed, but all the others run two carriers, providing seven traffi c channels plus the control channel. “It’s enough for the system”, he continues. “But of course we calculated that before they decided to make up the system. We analysed their analogue traffi c, especially the telephone traffi c. Duplex calls between two terminals take-up the most capacity – it’s two slots. But with a telephone, we need only one slot.” Most radio communication takes place through group calls, he adds, but individual calls can also be made.


Managing the mine Entering the main control room for the mine, we fi nd a spacious, modern mission-control centre with a huge video wall displaying an animated diagram of the mining systems and processes. T ree small links are fl ashing. From this room the duty engineer gives directions as to how the mine is to be operated, which machines are used, where to dig coal and so on. Mining is currently taking place at two working areas in the pit, according to the needs of the power station. One of these areas is expected to reach exhaustion in 2018 and the other in 2037.


Radio gateways integrate the mine’s remaining analogue talkgroups with the TETRA network. A Vertex Standard mobile is seen at the top of this rack


In front of the big screen sit three managers, again using the dispatcher terminal developed by Consortia. Each is equipped with three computer screens, a large telephone panel with an array of push-buttons, and a desk-mounted Motorola TETRA radio. A discussion about the TETRA system begins, and the duty engineer highlights a factor which been causing diffi culty for some users. With the old analogue radios, users could simply press the PTT button and speak immediately. But when you press the TETRA PTT to talk to someone, he says, you must wait for the prompt signal before you begin to speak. T is delay is actually very slight – about one-third of a second – though it increases to half a second when an analogue gateway is involved, because of the tone-signalling used on the analogue side. One of the managers explains that radio communication


Left: In the workshop is one of the special mining telephones which are installed in the mining


machines. The large keypad is designed for gloved hands.


A TETRA interface developed by


system integrator Consortia enables


the phone to make and receive full-


duplex voice calls via the radio network. It supports all normal telephone features,


including memories, last-number


redial and the 112


emergency number, explains Wojciech Rabczuk, who


programmed it all 34


The mine’s TETRA network shares this tower with one of the public cellular operators. At the top can be seen a stack of four Amphenol Jaybeam dipoles. A second stack is on the far side, allowing diversity reception


is extremely important in mining and that every single word counts. T erefore, if a radio user forgets to wait for access to the channel, the fi rst words may be lost, and they could be important ones. However, Wojciech Jurenczyk comments that his department has carried out many, many training sessions to familiarize users with the new system and accustom them to how it feels. In any case, any remaining diffi culty will be temporary because, in another year or so, the remaining analogue radios will be replaced with digital and the additional delay will disappear. But, as regards the TETRA system


itself, has Wojciech been satisfi ed with its performance? “Tak, tak, tak”, he answers – “Yes, yes, yes. T ere have been no problems!”


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