Dial-Up Troubleshooting Logic Your modem does not respond when attempting to dial out. You try another modem on another computer and the result is the same (no dialing). What is the most likely root cause?

Introduction / Context:
Effective troubleshooting isolates variables. When multiple devices and systems show the same failure, the shared dependency is suspect. With dial-up modems, the public switched telephone network (PSTN) line is a common external dependency beyond the PC and modem hardware.

Given Data / Assumptions:

• Two different modems and two different computers were tested.
• Both attempts failed to dial out in the same manner.
• The telephone line is common between tests (same service or jack).

Concept / Approach:

If different hardware and software platforms reproduce the same symptom, the problem likely resides in the external line: no dial tone, line dead, incorrect cabling, or service outage. This aligns with the principle of controlling variables to locate the failing link in the chain.

Step-by-Step Solution:

Verification / Alternative check:

Line testers or a simple analog phone can validate dial tone, polarity, and noise. Modem logs often show “NO DIALTONE” when the line is dead or miswired (e.g., plugged into PHONE rather than LINE jack).

Why Other Options Are Wrong:

Defective modem / defective computer: Unlikely since different units show the same issue. Software bug: Cross-system repetition reduces probability. Virus: Not a typical cause of identical modem failures across two systems in basic dialing tests.

Common Pitfalls:

Ignoring the physical line; misconnecting the wall cable to the PHONE jack; not checking for PBX or tone/pulse settings; overlooking line filters or splitters causing issues.

Final Answer:

bad phone line