Using the Hayes AT command set with a modem, which command resets the modem to its default or stored profile?

Introduction / Context:
Classic dial-up modems implement the Hayes AT command set. Knowing core commands is useful for legacy integration, embedded systems, and troubleshooting serial links. Resetting returns a modem to a known configuration state, often solving erratic behavior.

Given Data / Assumptions:

• We are working with Hayes-compatible AT commands.
• Goal: reset the modem to defaults or a stored profile.

Concept / Approach:
ATZ is the standard reset command. It reinitializes the modem, typically loading the default profile from NVRAM (often &F or &Y-based). Other strings serve different purposes: ATR is not a reset standard; DTR (Data Terminal Ready) is a serial control signal, not an AT command; DCE is a device role term (Data Circuit-terminating Equipment), not a command.

Step-by-Step Solution:
Identify the Hayes reset keyword: ATZ.Recall behavior: load default/stored settings and reinitialize.Select ATZ as the correct answer.

Verification / Alternative check:
Modem manuals list ATZ and AT&F (factory defaults) as standard reset/initialization mechanisms, commonly used in initialization strings.

Why Other Options Are Wrong:

• ATR: Not a standard reset command.
• DTR: A control signal line state, not an AT command.
• DCE: A device role term, not a command.
• None of the above: Incorrect since ATZ is correct.

Common Pitfalls:
Confusing ATZ (reset) with AT&F (load factory defaults). Both reset state, but ATZ uses stored profile; AT&F forces factory baseline.

Final Answer:
ATZ