Do the three standards work interchangeably?
Unfortunately, no. The three standards require both ends of the communication link to be compatible with the standard. This means that the ISP’s dial-in servers and the subscriber’s modem need to have the same standard, whether it be K56flex, x2, or v.90. Generally, none of the standards are interchangeable. If the ISP has K56flex and the subscriber has x2, communication at 56K speed is not possible. Recently, some modem manufacturers have been selling x2 and K56flex modems with the promise of a free or for-a-fee upgrade to the universal v.90 standard when the software to upgrade the modem is available. Also, some v.90 modems may be backward-compatible with either one of the older standards – but not both! If you have questions about whether your modem is compatible with or upgradable to any of the 56K standards, please contact your modem manufacturer or computer dealer for details.
