Bruel & Kjaer Type 2231, Modular Precision Sound Level Meter. 
Microphone Type 4189 
Attenuator ZF 0020 
Application Module BZ 7100
JJ 2614


**Turns On, seems to be in working condition. No further testing was done**
Signs of usage, paint chips and fading. Actual Pictures, you get what you see.



Features

  • Fulfills IEC 804 type 1, relevant sections of IEC 651 type 1 I, and ANSI S1.4-1983 type 1.
  • Easy to read liquid crystal alphanumeric and quasi-analogue display.
  • Selectable polarization voltage allows use of almost any microphone in the Bruel & Kjaer range.
  • RMS and Peak detection in parallel.
  • 73 dB Pulse range; 70 dB RMS Linearity range.
  • 24 to 113 dB (A) measuring range (30 to 133 dB (A) with attenuator) in 7 overlapping sub-ranges.
  • A, C, Lin. and All-pass weightings.
  • Extra wide all-pass frequency range allows infrasound and ultrasound measurements.
  • Internal memory has back-up battery power which prevents loss of application software and data when the instrument is switched off.
  • Facility for connection of Bruel & Kjaer Serial Interface communication port, allowing external control and output of measurement data.