This hearing aid primer is designed to define the differences among the three levels of hearing instrument technology: conventional analog circuit technology (most basic), digitally programmable/analog circuit technology (moderately advanced), and fully digital technology (most advanced). Both moderate and advanced technologies mean that hearing aids can now be programmed with a computer for various listening situations. Both advanced technologies may offer multiple channels and multiple microphones. Both advanced technologies allow the audiologist to shape the hearing aid's responses to various listening situations and gives the user more control over the hearing instrument.