Three) GSM. At the time, full mobile number portability was not available to TACS customers and the (088) prefix was closed. An automatic voice message was left in place for 12 months advising callers of the customer's new prefix. Frequency bands used by ETACS in the UK TACS BAND Summary ESNs were issued in batches of 65535 by BABT for phone manufactures to program into each cellular phone to make each one unique to the TACS network with which it attempted to register. The following countries had more than two batches of ESNs allocated to them: UK, Italy, Austria, China, Malaysia, Hong Kong, Singapore, Bahrain, UAE, Kuwait, Philippines, Sri Lanka, Australia. UK ETACS and US AMPS compared Commercial deployments References History of telecommunications History of mobile telecommunications in the United Kingdom Mobile radio telephone systems