This high-impedance piezoelectric earphone connects to crystal radios and other circuits with weak audio output. Use this high impedance crystal radio earphone where a standard earpiece loads the signal too heavily. Its 20,000-ohm impedance works with passive crystal radio signals without requiring a battery or separate amplifier. The ceramic element responds to the receiver's small audio signal. A 42-inch twisted black lead ends in two pre-tinned bare wires for soldering or terminal connections. The long cable leaves room to position the earpiece at the bench. Use the single earpiece for crystal radio builds, transistor radio restoration, lab demonstrations, and signal tracing. Use the bare leads in radio projects or connect them to screw terminals and breadboard jumpers. One beige earphone comes with two bare wire ends. Add a plug or terminals if your circuit needs them; the radio receiver isn't included. Use this earpiece when a crystal receiver produces too little output for a standard low-impedance headphone. Its ceramic element responds without adding a battery or amplifier to the circuit. The long twisted cable gives you room to work at the bench. Two tinned wire ends connect to solder points or screw terminals. Check for a high-impedance audio output before use. You receive one beige earpiece without a plug or radio parts.