Multimeter DT-830A, DT-830B, DT-830D comparison

Some kind of simple comparison of these multimeters and what features they have.

DT-830A
  DCV 200m-500
  ACV 200-500
  DCA 2000μ-200m
  Square wave generator
  BATT 1.5 9
  Diode
  Ohm 200-2000k
  No probe sockets, probes not detachable
  No buzzer?

DT-830B
  DCV 200m-1000
  ACV 200-750
  DCA 200μ-200m + 10
  hFE NPN PNP
  Diode
  Ohm 200-2000k
  3 probe sockets - 10ADC, V/Ohm/mA, COM
  No buzzer
  
DT-830D
  DCV 200m-1000
  ACV 200-750
  DCA 200μ-200m + 10
  hFE NPN PNP
  Square wave generator - note, some of them have this
  Diode
  Ohm 200-2000k
  3 probe sockets - 10ADC, V/Ohm/mA, COM
  Buzzer

About square wave: https://www.youtube.com/watch?v=4yfq9YrUUpI