If you are not sure what system your local phone uses please contact your local service provider for more information. Currently there are companies that operate both GSM 900 and GSM 1800 in Northern Cyprus although GSM 900 has far greater penetration. If your phone does not support these two bands you will not be able to use your phone here, even if you company has an agreement with a Northern Cyprus company to conduct roaming services. If you have a quad band phone (This is a phone that supports all four flavours of GSM, 850, 900, 1800, and 1900) you will be set for service in North Cyprus. Depending on where you live tri band phones can be tricky for not all of them have the same combinations. That is to say that some may be 850, 900, 1900 and others may be 900, 1800, 1900. Basically they can come in all possible combinations of the three flavours. Make sure that the Northern Cyprus standard is in one of the combinations. Ideally GSM 900 has the most coverage here.
Also you might want to know that since roaming charges can be quite costly if you will be staying here for a while or intended on making constant use of your phone you might want to by a local sim card. The local sim card will let you use your phone locally without the roaming charges, although you will also have a new phone number while you use the new sim card. However, please note that the gsm provider from which you purchased your phone may have locked (branded) your phone. If this is the case you will not be able to swap sim cards, unless you unlock the phone or have purchased an unlocked phone.
For up to date information on what is necessary for your roaming needs and the mobile telephony service in Northern Cyprus please click on the following link www.gsmworld.com