ERRATA: Revised Modulation Select (AT+MS) Command (this sheet replaces section In manual on this topic) This extended format command selects the modulation, optionally enables or disables automode,and optionally specifies the highest and lowest connection rates using one required subparameter and up to three optional subparameters. The command format is: +MS=[,[][,[][,[]]]] The default value as reported by the +MS? command is: +MS=11,1,300,28800 (DEFAULT) Subparameters are defined as follows: 1. = a decimal number which specifies the preferred modulation (automode enabled; see ) or the modulation (automode disabled; see ) to use in originating or answering a connection. The options are as shown below: Modulation Selected Possible rates (bps) 0 V.21 300 1 V.22 1200 2 V.22bis 2400 or 1200 3 V. 23 1200* 9 V.32 9600 or 4800 10 V.32bis 14400, 12000, 9600, 7200, or 4800 11 V.34 28800, 26400, 24000, 21600, 19200, 16800, 14400, 12000, 9600, 7200, 4800, or 2400 (DEFAULT) 64 Bell 103 300 69 Bell 212 1200 74 V.FC 28800, 26400, 24000, 21600, 19200, 16800, 14400 *For V.23, originating modes transmit at 75bps and receive at 1200bps; answering modes transmit at 1200bps and receive at 75bps. The rate is always specified at 1200bps. The modem may also automatically switch to another modulation (automode), based on the following restrictions: . The modem cannot automatically switch from the current modulation (specified by ) to some other modulation. For example, there is no standard way to automode from Bell 103 to V.23 . The DTE may disable automode operation (see ). . The DTE may restrict the range of modulations available by specifying the lowest and highest rates (see and below). 2. =an optional numeric value which enables or disables automatic modulation negotiation. Options are: Option Selected 0 Automode disabled 1 Automode enabled The default value is enabled for ITU-TSS compliant modulations, however, there are non-compliant modulations for which there is no automatic negotiation defined. For = 0 (automode disabled, i.e. fixed modulation): a. If is within the rates supported by the selected modulation, the selected rate is that specified by . Example: AT+MS--9,0,1200,4800 specifies V.32 4800bps fixed rate. b. if is greater than the highest speed supported by the modulation specified by , the starting rate is the highest rate supported by the selected modulation. Example: AT+MS=9,0,2400,14400 specifies V.32 9600 or 4800bps. c. To mimic NOS37=x operation, specify the and both to be the same requested speed, and to be the known modulation for that speed. Example: to select V.32bis 12000bps fixed mode (N0S37=10), issue: AT+MS=10,O,12000,12000. For = 1 (automode enabled) a. if is greater than the highest rate supported by the modulation specified by , the modem automodes down from the highest rate of selected modulation. Example: AT+MS=10,1,1200,24000 specifies automoding down from V.32bis 14400bps. b. To mimic NIS37=x operation, specify the modulation and the rate to start automoding down from using and , respectively. Set to 300 to allow automoding all the way down to V.21 300bps. Example: AT+MS=11,1,300,16800 selects automode starting at V.34 16800bps (no comparable S37 command). 3. = is an optional numeric value which specifies the lowest rate at which the modem may establish or maintain a connection. The value is decimal-coded in units of bps, e.g., 2400 specifies the lowest rate to be 2400bps. The default is 300 bps. 4. = is an optional numeric value which specifies the highest rate at which the modem may establish or maintain a connection. The value is decimal-coded in units of bps, e.g., 14400 specifies the highest rate to be 14400bps. The default is 2800 bps. Selected +MS Options The modem can send a string of information to the DTE cousisting of selected opdons: +MS? The response is: +MS:,,, Example: +MS: 9, 1, 1200, 14400 Supported Options The modem can send a string of information to the DTE consisting of supported options. +MS=? The response is: +MS: (list of supported values), (list of supported values), list of supported rate values) Example: +MS: (0, 1, 2, 3, 9, 10, 11, 64, 69, 74), (0,1) (300-28800), (300-28800) Part # I. BXXX Rev. 1.0 12/94