'Chipped' cellphones

Here in Ireland there are two major cellphone networks: Vodafone and Digifone. Each sells handsets from the major phone manufacturers when you open a cellphone account. Problem is, if you have a Digifone SIM card, it won’t work in a Vodafone phone, and vice versa. The handsets have been ‘chipped’ in some way. Does anyone know how this is done - hardware or software - and if it is reversible?

You mean “Provider Specific” phones. This is done for the phone companies by the manufacturers. Even if you get a “sim free” phone ie just the handset it will only (probably) work with the phone company it was intended for. We had this situation recently and had to order a “sim free sim free” phone. which is apparently the name that is given to a phone that will work with any network.

In the UK in the 90’s “Chipped” meant a phone that had had it’s sim replaced - they used to be non-removable.