Editing Answering machine (section)

== Combined operation ==
This refers to analogue sites, which support voice, fax and data transmission via landlines by adhering to specific protocols established by the [[ITU-T]]. Any incoming call is not identifiable with respect to these properties in advance of going "off hook" by the terminal equipment. So after going off hook the calls must be switched to appropriate devices and only the voice-type is immediately accessible to a human, but perhaps, nevertheless should be routed to a TAD (e.g. after the caller has identified itself, or has been identified by a recognized [[caller ID]]).

Starting with the integration of faxing devices into computers via [[Fax modem]]s the automated answering of voice calls by a computer went live via specific software, such as TalkWorks. These systems allowed for quite elaborate voice box systems, navigated via [[dual-tone multi-frequency signaling]], allowing a computer on a (single) telephony line to sound like a professional telephony system with hierarchical fax and message boxes with an [[automatic call distributor]], where a caller might deposit his messages, leave his faxes behind, might listen to specific messages, or start a fax-back service.

[[File:Elsa-Voice+Fax-Box-Modem.jpg|thumb|MicroLink Office, a voice-fax-data modem with standalone voice/fax box functionality]]

Besides these solutions, which primarily required a constantly running computer since a wake-on-ring function then (~1995) would take increasingly longer times to boot up an operating system, a few so-called ''selfmodems'' were available from such companies as [[USRobotics]] or [[ELSA Technology]]: the ''Sportster MessagePlus'', the ''56K Message Modem External'', and the ''MicroLink Office''. These devices answered incoming calls by playing a welcome message while discriminating fax calls (CNG-tone at 1100&nbsp;Hz) from voice calls, storing an incoming fax, or a voice message, respectively. A computer was only necessary afterwards to retrieve the faxes, or for storing the voice messages. In case of a full storage the devices changed their welcome message to another, prerecorded message, played upon answering an incoming call, possibly explaining that a message cannot be taken at the present time.