This page discusses the GSM mobile telephony system, which is increasingly popular and established throughout the world. The term GSM usually means the GSM standard and protocols in the frequency spectrum around 900MHz. There is also DCS1800 - GSM protocols but at different air frequencies around 1800 MHz - and in the United States, where spectrum for Personal Communication Services (PCS) was auctioned at around 1900MHz, operators using the aptly-named GSM1900 are competing against a plethora of other standards. As a result of this, the original and most widely-used GSM frequency implementation is also becoming known as GSM900, and DCS1800 is also known as GSM1800. However, although the physical frequencies used differ, the protocols and architecture remain the same. Repair Codes. Repair codes and problem found codes are to be used for all repairs performed on V3 phones. The repair code and the problem found code must be entered on your service link claim or the claim will be rejected. If multiple repairs are performed simultaneously on a particular V3 unit then all associated repair codes and problem found codes must appear on the service link claim.