S Registers

　　S registers are locations in a modem where settings are stored or status information can be examined. Modems can have dozens of S registers, while only the first 12 or so are standard. S registers are set by issuing ATSN=xx to the modem. N is the number of the register being set, while xx is the value the register is set at. For example, the register S0 determines how many rings the modem answers after.