Most dual SIM models work in alternate mode. Despite the fact that there are two cards, there is only one radio module. In other words, although both SIM cards are online, capable of receiving incoming calls and SMS, a conversation is possible only on one of them, and the other becomes inactive at this time. One SIM card in this case is the main one, outgoing calls are made from it and text messages are sent. Which card to be the main one is determined by the user himself. To do this, you either need to press a special button or restart your phone (the cheapest models work according to this principle).

Another thing is the simultaneous operation mode, when both SIM-cards are always active. In this case, there are two radio modules in the phone at once, and the exposure increases, although not necessarily twice. So if you are afraid of radiation from a mobile phone, consider whether it is worth buying a model with two radio modules? Consider how important it is to have two numbers online at the same time.

There is an opinion that it is safer to carry two phones with you than one “double”. Although both devices are always with you, at the time of the conversation you bring only one radio module to your head. However, no one can provide conclusive evidence that this theory is correct. And who knows if two separate phones do more harm than one with two radios? However, so far no study has conclusively confirmed or refuted even the very fact that mobile phones are harmful.