The SD card has an invalid file format, or the speaker wire connection is bad.
Before diving into the manual’s operational chapters, identify your exact AMT-78 variant. The model number typically appears on the rear panel or under the battery compartment. Most AMT-78 user manuals are structured into six core sections: amt-78 user manual
The AMT-78 is pre-configured for a default operational window (often around 78 seconds) . The SD card has an invalid file format,
Check probe connections or shield the testing area from wireless signals. Recalibration Schedules amt-78 user manual