There are several Motion Detector models:

Go Direct® Motion Detector (GDX-MD)
Made of gray plastic and cube-shaped. Teal label is printed with Go Direct Motion. This sensor connects to your device using bluetooth or USB cable. More information about Go Direct sensors: https://www.vernier.com/go-direct.
Compatible Software: Graphical Analysis 4 or LabQuest 2 App
Minimum Sensing Distance: 15 cm
Started Shipping in March 2018.
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Motion Detector (MD-BTD)
Green plastic, one LED on the right below the gold screen, track mode switch under pivoting head. Motion Detector 2 printed on lower body, as well as Vernier logo printed near the bottom. It began shipping January 2005. This Motion Detector shipped with a cable to connect it to any version of LabQuest, LabPro, SensorDAQ, or CBL2.
Compatible Software: Logger Pro, Logger Lite, Graphical Analysis 4 or LabQuest App
Minimum Sensing Distance: 15 cm
Started shipping 2005.
How old is my Motion Detector 2?
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Original Motion Detector (MDO-BTD, discontinued)
Blue plastic, two LEDs below and to the left/right of the gold screen. Motion Detector printed on lower body above Vernier logo impression. This Motion Detector shipped with a cable to connect it to any version of LabQuest, LabPro, SensorDAQ, or CBL2.
Compatible Software: Logger Pro, Logger Lite, Graphical Analysis 4 or LabQuest App.
Minimum Sensing Distance: 50 cm
Started shipping 2001 and discontinued in 2005.
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Ultrasonic Motion Detector for ULI (MD-ULI-O, discontinued)
Blue plastic, no pivoting head, non-detachable cord ending in a clear telephone connector, one red LED below the gold screen. Printed with the words Ultrasonic Motion Detector on body. For use with LabQuest, LabPro or SensorDAQ, or CBL2, the CBL Adapter for ULI Motion Detector, order code CBL-RJ11 [discontinued] is needed.
Compatible Software: Logger Pro, Logger Lite, or LabQuest App. This version does not Auto-ID, so it will only work with Graphical Analysis 4 by data sharing from LabQuest 2 or Logger Pro.
Minimum Sensing Distance: 50 cm
Started shipping 1994 and discontinued in 2015.
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MPLI Motion Detector (MD-M, discontinued)
Blue plastic, no pivoting head, non-detachable cord ending in a round DIN connector, one red LED below the gold screen. Printed with the words Ultrasonic Motion Detector on body. For use with LabQuest, LabPro or SensorDAQ, or CBL2, the CBL Adapter for MPLI Motion Detector, order code CBL-8MC [discontinued] is needed.
Compatible Software: Logger Pro, Logger Lite, or LabQuest App. This version does not Auto-ID, so it will only work with Graphical Analysis 4 by data sharing from LabQuest 2 or Logger Pro.
Minimum Sensing Distance: 50 cm
Started shipping 1994 and discontinued in 1999.
3269-md-uli-o.jpg


CBL Motion Detector (MD-CBL-O, discontinued)
Blue plastic, no pivoting head, non-detachable cord ending in white BTD connector, one red LED below the gold screen. Printed with the words Ultrasonic Motion Detector on body. This Motion Detector shipped with a cable to connect it to any version of LabQuest, LabPro, SensorDAQ, or CBL2.
Compatible Software: Logger Pro, Logger Lite, or LabQuest App. This version may or may not Auto-ID. If it does AutoID it will work with Graphical Analysis 4 directly, but if it doesn’t it will only work with Graphical Analysis 4 by data sharing from LabQuest 2 or Logger Pro
Minimum Sensing Distance: 50 cm
Started shipping 1996 and discontinued in 1999.
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Go! Motion (GO-MOT)
Go!Motion is functionally identical to the Motion Detector, and it adds a USB port for direct connection to a computer (Mac, Windows, or Chromebook) or LabQuest via USB cable. For use with LabQuest, LabPro, SensorDAQ, or CBL2, the Digital Sensor Cable (MDC-BTD) (same cable as a standard Motion Detector), can also be used. For use with calculators, four AA batteries are required.
Compatible Software: Logger Pro, Logger Lite, Graphical Analysis 4 or LabQuest App
Minimum Sensing Distance: 15 cm
Started shipping 2005.
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In addition, there are two models from Texas Instruments:

CBR 2 (CBR2)
White and gray plastic with mode switch under the pivoting head. The CBR2 is functionally identical to the Go!Motion. The only difference is the branding and the cables that are included in the package. It normally shipped with two cables. One was a calculator link cable to connect it to a TI calculator. The other was a cable to the mini-USB connector on any model TI-84 Plus calculator or TI-Nspire handheld. If you want to use the CBR2 with a computer (Windows, Mac, or Chromebook), you can use a standard USB cable LabPro USB Cable, order code CB-USB, $5. This type of cable is available at any computer store. For use with calculators, four AA batteries are required unless a CBL 2 interface is also used. For use with LabQuest, LabPro or SensorDAQ, or CBL2, the Digital Sensor Cable, order code MDC-BTD, $5 (same cable as a standard Motion Detector), is needed.
Compatible Software: EasyData, DataQuest, DataMate, Logger Pro, Logger Lite, Graphical Analysis 4 or LabQuest App
Minimum Sensing Distance: 15 cm
Started shipping 2005.
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CBR (discontinued)
Dark gray plastic. The sensor portion of the CBR is functionally identical to that in the Original Motion Detector, but this unit is made specifically to work with calculators. It normally shipped with a calculator link cable to connect it to a TI calculator. For use with calculators, four AA batteries are required unless a CBL 2 interface is also used. For use with the LabQuest series of interfaces, LabPro or SensorDAQ, or CBL2, the Digital Sensor Cable, order code MDC-BTD, $5, is needed.
Compatible Software: EasyData, DataQuest, DataMate, Logger Pro, Logger Lite, LabQuest App, Graphical Analysis 4.
Minimum Sensing Distance: 50 cm
Started shipping 1997 and discontinued in 2004.
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RELATED TIL
Which motion detector should I buy? What are the differences between them?