Mobile manufacturer Motorola is backtracking on recent comments by its spokesman suggesting that GPRS, the high-speed successor to GSM, might have to be made slower in order to stay within radiation absorption guidelines. Motorola marketing manager Rainer Lischetzki recently told New Scientist that implementing GPRS at the speeds its marketing division has hyped -- between 27Kbps and 86Kbps -- could cause a phone to overheat. He also said such speeds could push a phone's microwave radiation beyond European guidelines on the energy that can be absorbed by the brain. But Motorola now says the New Scientist report was at fault, claiming that Lischetzki is not "qualified" to discuss GPRS issues despite the fact that he is Motorola's technical marketing manager for GPRS. ZDNet's request for an interview with Lischetzki was refused. According to Motorola's director of communications Mark Durrant the company is not prepared to risk "another inaccurate report". Instead Motorola has issued as statement conceding that: "Whilst the initial GPRS phones that enter the market may not operate at their highest theoretical data speeds, that fact is not related to the issues raised by New Scientist." Motorola offers no explanation about why higher speeds will not be available. However the Department of Trade and Industry (DTI) confirmed that higher speeds could be potentially dangerous. "It is conceivable that GPRS devices... could produce exposures above the levels specified in the Council Recommendation," said a DTI spokesman. Simon Mann, technical spokesman for the National Radiological Protection Board (NRPB) agrees, saying that although mobile manufacturers will have to observe regulations governing the emissions from mobile phones, it is "entirely feasible" that some GPRS mobiles, particularly those at the top end of the market, could tip over the [emission] limits". The issue revolves around whether or not GPRS mobile phones will operate at the speeds mobile manufacturers are touting. Typically GPRS mobiles are hyped as transferring data at around three to five times faster than current mobiles, although consensus suggests these speeds are exaggerated. Analogue mobile phones have a transmitter which is on all the time when making a call, with one phone having exclusive use of one radio channel. GSM phones share channels, with up to eight phones taking it in turns to transmit short bursts of data on a single channel. This means that although a GSM phone has a maximum power output of two watts, in practice it transmits an eighth of that -- quarter of a watt, maximum. This can and frequently is reduced still further. To save battery life and to increase the number of phones that can be handled by the system, the mobile's power is automatically adjusted to the minimum necessary to keep a reliable link with the base station. GPRS uses exactly the same system, but to increase the amount of data transferred a phone can use more than one slot. Thus a three-slot GPRS link, carrying around 30 to 40kbps, will use a maximum of three-quarters of a watt. This is roughly the same as an analogue phone used for a single voice call, but as with GSM the power levels will often be lower than the maximum especially in areas with a high density of base stations or a low density of buildings. Average power levels are further reduced by GPRS being a packet-based system -- the transmitter is only on when data is being sent and is idle otherwise. A file transfer from the phone to the base station will make the transmitter work at full tilt -- keystrokes or Web browsing will only fire up the transmitter occasionally, reducing the average power output to a few milliwatts. When ZDNet eventually got to speak with Lischetzki, he said confusion over what speeds GPRS would actually run at were damaging both for Motorola and for the mobile industry in general and that his comments about the safety of GPRS mobiles were misconstrued. He offers no clarification on theses comments. Motorola's refusal to answer questions was condemned by the Consumers' Association. "Given the concern among consumers about health issues and mobile phones, I think Motorola's actions are unhelpful," said a spokeswoman. She added: "Clarity is needed on these issues. It's a topic of concern for many consumers." To have your say online click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.