8518.40 - Audio-frequency electric amplifiers:

HTS Code 8518.40 specifically classifies audio-frequency electric amplifiers. These devices are designed to increase the amplitude or power of audio signals, making them suitable for various applications such as home stereo systems, public address systems, and musical instrument amplification. The core function is signal amplification within the audible frequency range.

This category is distinct from its sibling entries within HTS 8518. While 8518.10 covers microphones (input devices for sound), 8518.30 deals with headphones and earphones (output devices for listening), and 8518.50.00.00 encompasses complete electric sound amplifier sets. 8518.40 focuses solely on the amplifier component itself, separate from integrated sets or other audio input/output devices.

Within HTS 8518.40, two subcategories exist: 8518.40.10.00 for amplifiers used as repeaters in line telephony, and 8518.40.20.00 for all other audio-frequency electric amplifiers. This distinction is crucial for tariff purposes, as specific uses, like telephony, may have unique tariff treatments or require detailed technical specifications for accurate classification.