The HD-4ASH, HD-4SP and HD-4HS Craft Test Sets feature an amplified speaker that lets the technician listen "hands-free," as well as tone and pulse dialing, a line-polarity indicator, and a built-in electronic ringer. HD-4ASH is also line-powered and does not need a battery for the amplified-speaker function. That model and HD-4HS also include a headset.
HD telecom Inc.
Fort Collins, CO