Because term of a contract (buy on the installment plan payment) does not expire, it is named 'red'. Recently slightly unfamiliar what's called 'red ROM' points to cell-phone and smartphone which user sold to used goods distributor before it is for the expiration in term of a contract. User purchases cell-phone and smartphone which carrier locks SIM and sells, and thing said to be white ROM in used business points to cell-phone and smartphone which we sold to used goods distributor for (cancellation such as two years restrictions and terminal blanket purchase) at the time of the expiration in term of a contract. Therefore, as for the word white ROM, white, contract information are filled out in cell-phone and SIM where black, contract information are not written in at in SIM contracted with not smartphone for SIM, but express SIM which does not become active with ash. Therefore we cannot use voice call and the Internet if we do not insert SIM card. Phone numbers are not written in at the cell-phone and smartphone body directly, and contractor information comes to be written in at SIM card recently. Such a white ROM is sold in auction site or mail order site. Model change when canceled, all information is removed, and information is not written in at ROM. In contrast, ROM that contractor information is not written in at the cell-phone body and ROM of the cell-phone is called white ROM. Thing contracting in portable shop is basically all black ROM. Carrier is available for recognition that we contract, and such an information makes possible voice call and email. Information such as phone numbers is written in at ROM of cell-phone which we usually use, and such an ROM is called black ROM.

It may be said that these are important differences that you should know in using SIM card. We may hear the word 'white ROM' and 'black ROM' when we use cell-phone and smartphone.

Black and white rom