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)