A.1 Modem Service Classes

Several Telecommunications Industry Association (TIA) modem control standards define services classes for a PSTN modem. Some of these are being made into international (International Telecommunications Union, ITU) Recommendations. (ITU was formerly known as CCITT.) Other organizations (including Microsoft) are also defining modem service classes (e.g. VoiceView). TIA and Portable Computer and Communications Associations (PCCA) are defining devices that look like modems for Cellular or private Wireless Networks.

The capabilities of the modem can be read, test and set using the AT+FCLASS command. The syntax to test the capabilities is AT+FCLASS=?. The modem will respond with ERROR if it does not recognize the command. If it does, the result will be one or more values separated by comma (0x3C) characters. A table of defined values and sources is presented here:

Table A-1.  Serial Device Standards and Service Classes

FCLASS Value

Specification

Description

0

TIA-602,

TIA IS-131,

ITU V.25ter

common data modem,

interim standard extensions

CCITT/ITU equivalent

(0)

PCCA XSTD-101

PCCA STD-101

Character Mode Wireless Modems

revision

1

TIA-578,

TIA-578-A

Service Class 1 FAX modem,

first revision of Class 1

1.0

ITU T.class1

draft CCITT/ITU equivalent

2

TIA SP-2388

obsolete Service Class 2 FAX modem

2.0

TIA-592,

ITU T.class2,

TIA IS-135,

TIA IS-99

standard Service Class 2 FAX modem

draft CCITT/ITU equivalent

TDMA Digital Cellular FAX modem (IS-54 network)

CDMA Digital Cellular FAX modem (IS-95 network)

8

TIA IS-101

Voice DCE (aka Service Class 8, or AT+V)

80

VoiceView 1.0

Voice View compatible modem (Radish Communications)