Mobile data terminal
|This article does not cite any references or sources. (July 2008)|
A mobile data terminal (MDT) or mobile digital computer (MDC) is a computerized device used in public transit vehicles, taxicabs, courier vehicles, service trucks, commercial trucking fleets, military logistics, fishing fleets, warehouse inventory control, and emergency vehicles, such as police cars, to communicate with a central dispatch office. They are also used to display mapping and information relevant to the tasks and actions performed by the vehicle such as CAD drawings, diagrams & safety information.
Mobile data terminals feature a screen on which to view information and a keyboard or keypad for entering information, and may be connected to various peripheral devices. Standard peripherals include two-way radios and taximeters, both of which predate computer assisted dispatching. MDTs may be simple display and keypad units, intended to be connected to a separate black-box or AVL (see below) computer. While MDTs were originally dumb terminals most have been replaced with fully functional PC hardware, known as MDCs (Mobile Digital Computers). While the MDC term is more correct, MDT is still widely used. Other common terms include MVC (Motor Vehicle Computer) and names of manufacturers such as iMobile or KDT.
In the earlier days of computer-aided dispatching (CAD), many MDT's were custom devices, used with specialized point to point radios, particularly in applications such as police dispatching. While applications like taxi and package delivery often still use custom designed terminals, majority of CAD systems have switched to rugged ruggedized) laptops and Wide-Area Wireless IP communications, utilizing the Internet or private IP networks connected to and over it.
For many industrial applications, such as commercial trucking, GIS, agriculture, mobile asset management, and other industries, custom electronic hardware is still preferred. Custom terminals use I/O interfaces that connect directly to industry-specific equipment. They are usually environmentally hardened packages with power supply protection and robust memory file systems that greatly improve reliability and task efficiency. MDT solutions that are based on ruggedized consumer products or consumer available software will typically not have the life cycle duration expected in industrial applications, over 5 years.
Typical MDT features
- 9 VDC to 36 VDC input power.
- SAE J1455 compliant.
- MDT should be tablet convertible
- Electrical transient protection, such as described in ISO 7637, Electrical disturbance on road vehicles.
- Serial port to connect to a satellite or terrestrial radio transceiver.
- Digital I/O to monitor external events.
- Removable medial or I/O port of retrieving data or upgrading software.
- Wide operating temperature -10 C to 60 C or better.
- Water & Dust tested as per IP65 certification.
- Drop tested to MIL-STD 810G, which specifies multiple drops from 48" to plywood over concrete.
- Sealed against dust and liquid.
- Connections to industry specific equipment, such as J1708 data bus for commercial truck applications.
- Display technology specific to viewing conditions for the intended industry (LCD, TFT LCD, Vacuum fluorescent display, CSTN).
- Integrated un-interruptible power supply, which will ride through electrical brown-outs typical in vehicle installations.
- Internal 802.11b transceiver (depending on target application), possibly with external antenna connection.
A related device classification, specific to the transportation industry, is called automatic vehicle location (AVL). Mobile data terminals are often used in conjunction with a "black box" that contains GPS receiver, cell phone transceiver, other radio devices, or interfaces to industry-specific equipment. AVL devices may be simple stand-alone modems or may include operating systems with application space for the system integrator.
MDTs are most commonly associated with in-vehicle use. This requires the MDT to be anchored to the vehicle for driver safety, device security, and user ergonomics.
Mounts are designed for attaching MDTs to mobile workspaces into most notably automobiles, forklifts, boats, and planes. Specialized manufacturers such as Gamber-Johnson and Havis (formally LedCo) build mounts for the specific MDT brands and models and for specific vehicles. Specialized regional metal shops and mount design integrators design MDT mounting hardware for low volume specialized applications such as forklifts and commercial boats.
MDTs generally require specific installation protocols to be followed for proper ergonomics, power and communications functionality. MDT installation companies such as PCN Strategies, USAT Corp. and TouchStar Pacific specialize in designing the mount design, assembling the proper parts, and installing them in a safe and consistent manner away from airbags, vehicle HVAC controls, and driver controls. Frequently installations will include a WAN modem, power conditioning equipment, and a WAN, WLAN, and GPS antenna mounted external to the vehicle.