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CHAPTER 5: Command Mode
Regarding the Series II Modem’s method of dialing, the Modem can
detect standard dial tones and busy signals. This capability (“smart
dialing”) allows the modem to wait for a dial tone, and when one is
detected, to begin dialing immediately.
The Modem also can detect a distant busy signal if, after dialing, it
reaches a busy number. This is useful because it allows the modem to
immediately abandon a call, rather than wait 45 seconds for a carrier
signal that will never come. S-Register S7 defines the wait for carrier
time (refer to Chapter 6).
The Series II Modem gives you a choice between the wait-for-dial-tone
(“smart”) method we just described, and blind (“dumb”) dialing, where
instead of detecting actual dial tones, the modem relies on timed
pauses. When the wait-for-dial-tone method is chosen, the busy signal
detection capability is also activated. The X command is also used to
select which dialing method is used.
Five different X commands are available (X0 through X4), with five
different effects on the Modem’s Result Codes.
X0 Provides the basic (short) result codes and provides
“dumb” dial capabilities.
X1 Provides the extended result codes and provides “dumb”
dial capabilities.
The remaining X commands affect Call Progress, and turn on Extended
Result Codes.
X2 Looks for dial tone only and will not provide a busy
response.
X3 Looks for busy only and not look for dial tone.
X4 Looks for dial tone and for busy.
The factory default setting is X0, which selects Basic Result Codes
and the blind (“dumb”) method of dialing.