S registers

S registers are information storage areas inside the modem. The AT command set users the S registers to configure modem options. Some S registers have default settings. For normal modem operations, the default settings are usually adequate. However, special circumstances might require you to change some defaults.

To change or read the value of an S register, begin the command with the letters AT.

To read the value of an S register, use the ATSr? command (r=register number 0-110).

For example, to read the value of S register 0, type ATS0? and press Enter.

To change the value of an S register, use the ATSr=n command (r=register number 0-110, n=the new value you want to assign).

For example, to change the value of S register 0 to 20 rings, type ATS0=20 and press Enter.

The following table summarizes the S registers:

Register	Function	Register value
S0	Auto-answer ring number	0-255 rings
S1	Ring counter	0-255 rings
S2	AT escape character (user-defined)	0-127 ASCII
S3	Command line termination character (user-defined)	0-127 ASCII
S4	Response formatting character (user-defined)	0-127 ASCII
S5	Command line editing character (user-defined)	0-127 ASCII
S6	Wait before dialing	2-65 seconds
S7	Connection completion timeout	1-255 seconds
S8	Comma dial modifier time	0-65 seconds
S10	Automatic disconnect delay	1-254 10ths of a seconds
S11	DTMF dialing speed	50-150 milliseconds
S12	Escape guard time	0-255 50ths of a second
S14	General bitmapped options status	Only bit 2 and bit 6 are used. Bit3: Result codes (Vn) 0=Numeric (V0) 1=Verbose (V1) Bit6: Pulse dial PPS selection (&Pn) 0=10 PPS (&p0, &p1) 1=20 PPS (&p2)
S21	V.24/General bitmapped options status	Only bits 3, 4, and 5 are used. Bit3-4: DTR behavior (&Dn) 0=&D0 selected 1=&D1 selected 2=&D2 selected 3=&D3 selected Bit5: DCD behavior (&Cn) 0=&C0 selected 1=&C1 selected
S22	Results bitmapped options status	Only bit 4, 5, and 6 are used. Bit4-5: result codes (Xn) 0=X0 selected 4=X4 selected 5=X5 selected 6=X6 selected 7=X7 selected
S24	Timer to control sleep mode	0, 5-65 seconds
S28	V.34 Modulation enable or disable	0=Disabled  1=Enabled
S30	Inactivity timer	0-255 minutes
S32	Synthetic ring volume	0-255
S33	Synthetic ring frequency	0-5
S35	Data calling tone	0=Disabled  1=Enabled
S36	Negotiation fallback	See S48
S37	Dial line rate	0=Auto rate  1=Reserved  2=1200/75 bit/s (V.23)  3=300 bit/s  4=Reserved  5=1200 bit/s  6=2400 bit/s  7=4800 bit/s  8=7200 bit/s  9=9600 bit/s 10=12000 bit/s 11=14400 bit/s 12=16800 bit/s 13=19200 bit/s 14=21600 bit/s 15=24000 bit/s 16=26400 bit/s 17=28800 bit/s 18=31200 bit/s 19=33600 bit/s
S38	K56flex downstream rate	0=Disable K56flex  1=Automatic rate selection  2=32 kbit/s  3=34 kbit/s  4=36 kbit/s  5=38 kbit/s  6=40 kbit/s  7=42 kbit/s  8=44 kbit/s  9=46 kbit/s 10=48 kbit/s 11=50 kbit/s 12=52 kbit/s 13=54 kbit/s 14=56 kbit/s
S42	Auto rate	This command is used for testing and debugging only. 0=Disabled 1=Enabled
S43	Auto mode	This command is used for testing and debugging only. 0=Disabled 1=Enabled
S48	LAPM error control and feature negotiation	7=Enabled 128=Disabled S48=7 S36=0, 2 LAPM or hangup S36=1, 3 LAPM or async S36=4, 6 LAPM, MNP or hangup S36=5, 7 LAPM, MNP or async S48=128 S36=0, 2 do not use S36=1, 3 async S36=4, 6 MNP or hangup S36=5, 7 MNP or async
S89	Timer to control sleep mode	0, 5-65 seconds
S90	Read-only local phone	0=on-hook  1=off-hook
S91	Line transmit level	6-15 dB
S108	Network codec type	22=µ-Law  33=A-Law  7 =V.8 information. Or choose on the basis of the country ID.