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.

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Black Box MD1640A, MD1641A manual Command Mode