n a different GSM cellular telephone when the card is inserted in that phone. This is an important feature because some GSM subscribers rely on cellular telephone rental to get coverage in different frequencies when traveling to remote countries. With on-card storage, they can take their messages home with them, even after they drop off their rented cell phones. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Short Message Service (SMS) Short Message Service (SMS) 20.5 EMS and MMS: Newer Short Message Standards EMS, the enhanced message service, is SMS with bells and whistles (literally). EMS al- lows ring tones, icons, and graphics to be sent to user terminals. EMS actually changes very little in the SMS system except for the receiving SME. The receiving SME must be equipped to receive, interpret, and display EMS messages. EMS has two functions, both intended for consumer use rather than for commercial business use. The first is that any subscriber who upgrades to an EMS-compatible cellular telephone can down- load custom ring tones, icons, and display images. The subscriber can customize the EMS cellular telephone to suit personal tastes. This is all done without any changes to the specifications for the SMSC or other SMS, GSM, or ANSI-41 network components. EMS simply uses concatenated, binary-encoded SMS messages to create the bells, whistles, icons, and images. The other use of EMS is that a subscriber equipped with an EMS-capable terminal can send EMS messages to other subscribers. These messages can include text and also have graphics or sounds inserted at any point. If the receiving SME is EMS-capable, then the message will display properly. However, if the receiving SME is a standard cel- lular telephone with traditional SMS capability, the message is likely to be garbled or to fail to display. Older units that are not EMS-compliant 