nes to control the addressing and Voice mail was one of the first voice processing applications de- selection of menu options. DTMF tones are also used to identify the veloped during the late 1960s. Voice mail, as the name suggests, caller. This means that usually only business users in the U.K. can allows callers to leave voice messages for other users of the system. take advantage of these systems. Typically connected to a PABX via a few analogue telephony However a limited number of systems support speaker dependent interfaces, these systems are widely used in North America where recognition technology to receive commands from callers. This is the large penetration of DTMF phones facilitates its use. very suited to voice mail systems since inherently the user has to The voice messages are usually short reminders or enquiries. The identify himself to the system initially by using a password. The person intended to receive the message is notified by a message speech recognition templates for that particular caller can then be waiting lamp on his/her telephone, or by a different dial tone when recalled and used. Command words can therefore be chosen to suit the recipient uses their phone. Sometimes a radio pager is used to customers on an individual basis. alert the recipient of new voice mail. One important aspect of a voice mail system is the management Inexpensive telephones with message waiting lamps are not as of the users, mail and system. When selecting a voice mail system readily available in Europe as they are in the USA. The other these features should play an important part of the decision. alerting systems are generally thought of as unsatisfactory or too Guide lines for the size of a voice mail system are difficult to expensive for widespread use. define, since the number of lines and disk size depends on the usage One popular use of voice mail is as an adjunct cellular telephones. of the system by users. However, for example, in a medium use Since cellular phones may be switched off for substantial 