This is the HD-1986 Microlizer.  This is a microphone pre-amp with built in equilizer.  Two controls allow you to adjust the Low Cut-Off at 490Hz + or - 12dB, and the High Cut-Off at 2800Hz + or - 12 dB.  Input impedance 100 kOhm, Frequency response 200Hz to 10kHz, Maximum input level 500mV.  Operates on one 9-Volt transistor battery.

This equilizer was desgned to be used with amateur radio to tailor the audio to match the user's particular voice.  Note that normal operation of this item does not continuously light the LED.  It is only used to check the battery upon power on.  It will then extinguish to help extend battery life.  This is normal operation.

This unit is fully functional, is in very good condition, and has no user modifications or added holes.  Includes a new 'Re-Issue' copy of the manual.