3Com PC Card manual Echo Commands, Hook Switch Control, Interrogate Modem Status

	AT Commands 29
,	Causes a delay, determined by S8, before the modem proceeds with the
	next command or digit.
=	Same as the ‘,’ modifier except that the delay is doubled.
!	Causes the modem to go on-hook for .5 second and then off-hook for .5
	second before continuing.
@	Causes the modem to wait until it detects 5 seconds of silence before
	continuing.
;	Causes the modem to go to the command mode when the number is
	dialed. In order to proceed with channel establishment mode ATO or ATD
	must be entered. Any characters that follow this parameter are treated as
	AT commands.
^	Do not send calling tone.
#	Causes a 0.5 second delay before the modem dials the digits (DTMF)
	following this modifier.
L	Causes the last telephone number that was dialed by the modem to be
	re-dialed.
S	Causes the modem to dial the number in stored position "n" Format is
	S=n or Sn. If S41 is set to a value other than 0, the modem will attempt a
	maximum of S41 redials upon call failure. In error correction mode S38
	dictates the delay before terminating a call (matched with S10).

E: Echo Commands

Defines whether characters are echoed back from the modem to the DTE when in command mode.

E0	Command echo inhibited.
E1	Command echo enabled.

H: Hook Switch Control

Controls the modem’s hook switch relay.

H0	Terminates a call.
H1	Causes the modem to go off-hook.
I: Interrogate Modem Status
I0	Requests the modem code.
I1	Requests that a checksum calculation be performed on the software
	ROM. The answer is displayed as four hexadecimal digits.