cell-phone-29-01_optMOBILE PHONE is now a days a common electronic device in everyones pocket. Generally it is used between two peoples to have voice communication between each other but can be used for short message service (SMS) and for many other featured contents. The sociological and psychological impact of this simple instrument is no doubt beyond the expectations. The pros and cons of cell phone is debatable but there is one technical factor which contains dark side only, Yes – the nuisance created by our beloved fairy wand tool is called electromagnetic interference.

“Switch Off Your Mobile Phone” in you daily life you will have probably seen such instructions/warnings on places like petrol pumps, hospitals and banks or even restriction is faced during travel in jet plane. The question can arise that why there are such limitations imposed on the mobile phone? The answer is hidden in the phenomenon which is known as electromagnetic interference (EMI). The EMI emitted from mobile phone can be hazardous to the following sensitive places and equipments.

Intensive Care Units:

Studies have been conducted all over the world to evaluate the effect of EMI caused by cell phone. The significance of problem is in direct relationship with signal power, if conditions are not favorable then phones are forced to operate at their maximal power limits (in the case of GPRS devices it is 2 watts).

In a particular study conducted by Academic Medical Center, University of Amsterdam, the research team examined the effects of General Packet Radio Service (GPRS) and Universal Mobile Telecommunications System (UMTS) signals on critical care equipment such as ventilators and pacemakers. Almost 50 EMI incidents were recorded where 75 per cent were found significant.

The question of safety is complex and in practice it is often confusing. Many implicit reports exist of interference with medical electrical equipments. However it is difficult to compare various study findings due to number of devices tested, non-uniform designs and heterogeneous technological information. With technological advancement, newer equipment is becoming less sensitive to interference as manufacturers are adopting increasingly stringent standards for screening. However the safest option is the “one meter rule” proposed by Werner Irnich and Tobisch R which suggested restriction of mobile phone use to greater than 01 meter from equipment.

Petrol filling stations:

The cell phone interference at a filling station can be dangerous and can cause fire/explosion. Some people dont feel that is true and this is considered as an urban myth, but the matter can be understood by proper scientific reasoning. A cell phone is a radio transmitter/receiver and it produces R.F. fields, the R.F. energy radiated from the transmitter will induce R.F. currents in surrounding conductive objects within its field. These R.F. currents can produce high voltages. Any voltage even low ones can cause sparks remember your 12 volt car battery produces several thousands of volts which is applied to the spark plugs. The risk of sparks caused by cell phones is small, very small indeed. However it is, nevertheless, a risk. That is why you are told to switch them off at filling stations. Another reason for this restriction is because not all mobile phones are “Intrinsically Safe” i.e. the electronic circuitry and battery is not completely sealed so that in theory a small spark could ignite fumes at the petrol station.

Restriction during air travel:

“Please turn off your mobile/cell phones during takeoff and landing as they may interfere with the airplane system” – A common instruction while on board a plane. A common belief among people is that such instruction is a worthless stuff but in reality there numerous scientific reasons that can be argued on this issue but before we proceed further let look into the opinion of Federal Communications Commission (FCC) which is an independent agency of the USA. The FCC bans the use of cell phones using the common 800-MHz frequency as well as other wireless devices (Wi-Fi, Bluetooth etc) during takeoff and landing this is expressed as “no electronics below 10,000 feet” rule. Federal Aviation Regulations (FAR) part 91 section 21 legally prohibits the use of PED (portable electronic devices) on any civil aircraft. Strictly speaking mobile phones do interfere with airplane communications and navigation networks, the potential risk of interference would be a more serious problem at a lower altitude. This is because towers might be miles below the aircraft forcing the phone to transmit at its maximum power and proportionally increasing the risk of interference. Even though aircraft wiring is shielded but specifically not all aircraft wiring is shielded/screened. In fact over time shielding can degrade or get damaged, due to the practicalities of corrective maintenance thus unshielded wires are more susceptible to interference caused by cell phone signals.

To sum up the topic under discussion one can conclude that more sensible use of mobile phone is required among masses in Pakistan. The people should know the pros and cons of cell phones and avoid their usage not only at places discussed above but also in banks, electronic sales counters etc. Most of the cell phone calls of longer duration are unnecessary and since mankind has managed to survive millennia without them why cant we use mobile phone more wisely to avoid any unpleasant situation.

The writer is Electrical Engineer in Karachi Nuclear Power Plant.

By Web Team

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