Enhanced Network Selection (sometimes referred to as Enhanced Network Service, or simply ENS) extends GSM by making it possible for a GSM cellular device (e.g., handset) to be "homed" OTA (over the air) to different networks. This makes it possible for Cingular Wireless

Cingular Wireless

AT&T Mobility LLC is a wholly owned subsidiary of AT&T that provides wireless services to 100.7 million subscribers in the United States, Puerto Rico and the U.S. Virgin Islands...

, while it is still operating two networks post merger with AT&T Wireless

AT&T Wireless

AT&T Wireless Services, Inc., founded in 1987 as McCaw Cellular Communications, Inc., and now legally known as New Cingular Wireless Services, Inc., formerly part of AT&T Corp., is a wireless telephone carrier in the United States, based in Redmond, Washington, and later traded on the New York...

, to "home" a given cellular device to either the "orange" (old Cingular Wireless) or "blue" (old AT&T Wireless) network. That can improve performance for certain customers because without ENS a GSM device will only select a non-home network when a "usable" home network signal doesn't exist, even when a non-home network has a better signal or when the home network has no available capacity.

For ENS to work, both an ENS-capable device and an ENS SIM are needed.

• Most mobile devices sold by Cingular from the end of 2004 should be ENS-capable.
• ENS SIMs are marked "64K". (Prior SIMs are no more than 32K. There is no other benefit to the increased memory in the SIM.)

Cingular states that any device to be activated in excess of 10000 quantity is required to support ENS.