Voice capabilities are not mandatory, but if present, the following requirements and recommendations apply.
There is a separate category of voice-only modem that can be integrated with a telset. These devices are not required to support data or fax, but the following requirements do apply.
12. Voice modem supports TIA-695 (AT+V)
Consumer PC 98
Office PC 98
Entertainment PC 98
Recommended
Recommended
Required
TIA IS-101-1994, the interim standard for Voice DCE, has been superseded by TIA-695. TIA-695 adds voice formats and speakerphone control commands. ITU-T plans an equivalent recommendation—V.voice—to be completed and assigned a number in January 1998. V.voice will add some small corrections to TIA-695, plus provisions for duplex voice. See also the “Voice modem supports full-duplex voice I/O” recommendation later in this section.
The following voice modem features are required:
13. Voice modem support includes PC 98 recommendations
| Recommended |
The following voice modem features are recommended:
14. Voice modem supports local telset interfaces
| Recommended |
For many voice applications, it is desirable for the PC and voice modem to be able to communicate with the person using the telset. This allows a consistent interface between local use and remote use, where remote means calling in from outside or using a cordless phone.
If the device is integrated with a telset, this is straightforward and a requirement; the handset and keypad are directly accessible within the device. If the device is not integrated with a telset, then there is a technical challenge. To gain access to the telset’s handset and DTMF keypad, the voice modem must be able to cut the connection from the telset to the PSTN, and then must provide power and signal coupling to that telset.
The difficulty is that the switchable-isolation means (that is, the relay) must be able to withstand real or simulated lightning strikes of 1750 volts (U.S. Federal Communications Commission [FCC] Part 68) to 3750 volts (German FTZ) without catching fire. Therefore, this is a recommendation rather than a requirement for data/fax/voice modems.
15. Voice modem supports simultaneous voice/data integration capabilities
Recommended
A profusion of solutions have been offered for simultaneous multimedia phone calls, including propriety solutions, semi-public solutions (DSVD 1.2 and V.34Q), and standard solutions (ITU V.61, V.70-suite, and H.324-suite). Meanwhile, standard IP-based solutions are the wave of the future. Microsoft NetMeeting™, for example, uses H.323.
Therefore, PSTN voice/data integration is not required for desktops or servers. H.324 is emerging as a standard for consumer installations. To support H.324, modems should support ITU V.80, V.8bis, and V.25ter Annex A.
Note: VoiceView is not supported in Windows 98 or Windows NT 5.0.
16. Voice modem supports speakerphone
Recommended
Audio I/O for speakerphone can be implemented in any of the following ways:
17. Voice modem supports full-duplex voice I/O
| Recommended |
TIA-695 was written for TAM applications, with extensions for control of speakerphone functions. In the latter case, the speakerphone adaptive echo canceller is in the modem DSP, and the audio I/O is directed to separate microphone and speakers.
TIA-695 does not address simultaneous voice playback and recording. The applications that need this include speakerphones using audio I/O in the PC, playback while listening for voice responses, and PTSN-to-IP telephony bridging.
Microsoft is collaborating with other members of TIA TR-30 and ITU-T SG16 to define an addition to the draft recommendation V.voice (that is, TIA-695) to support full-duplex voice. This work could be completed by January 1998. Microsoft support for this feature will be based on that ITU-T recommendation.