A portable device is one that can be carried for at least ten minutes without resting	For single handed carrying < 4.4 kg. For use held away from the body < 2.3 kg If manipulated with precision < 400 g The device should be sturdy and able to absorb a few knocks without sustaining any damage Handle and grip design is important. Design criteria exist. Straps, holsters, compatibility with clothing need to be checked for the naval environment e.g. being knocked against hatches, snagged in doors.
There is no holy grail for data input. Keyboards and controls must still be easy to use	The minimum key centre spacing should be 19 mm. Telephone keypads are better than calculator ones. Avoid numeric or cursor input for alphabetic entries. Macros can avoid long keying sequences.
The device must be easy to operate and hold	Operation with either hand should be possible. Room for finger grips is important. Operation should be with the wrist straight. Grips, rounded edges and texture help. 'Clipboard' devices can be given straps, handles etc. to improve ease of use.
Secondary features matter	Battery type, life, replacement need to meet the context of use. Connectors should not collect dirt, grease. Cables and probes should be easy to fit, use, stow.

The physical environment is very demanding	The device must handle a wide temperature range with rapid fluctuations. It will encounter a range of substances. It will be dropped and bumped into things. There are severe space restrictions and snagging hazards.
The organizational boundaries are flexible	New technology allows decisions to be made over what is done locally or remotely, onboard or ashore. The operator skill and training will need to reflect these decisions.
Technical compatibility may be difficult	If the same keying sequence has different consequences on the device, on the office PC or on the control console then operators are likely to make errors. Smaller devices may not use windowing interface conventions.

Many devices suffer from known shortcomings

The study team has seen devices with inadequate key spacing, membrane keys with no feedback, alarms that are too quiet, displays with no backlighting, long protracted keying sequences and awkward command combinations, collections of devices with snagging hazards, connectors that collect dirt and many other avoidable faults. The absence of research data may mean that devices fall short of the ideal, but major mistakes can be avoided on the basis of experience.

The risks can be identified

Most HFI methods use a risk-based approach. The principal risks can be identified.

There is a consistent definition of best practice for Human Factors	The Display Screen Equipment, Machinery Safety, Work Equipment Regulations have standards that give a consistent definition of Human Factors best practice. The definition is also given in standards relating to user-centred design. Regardless of the strict applicability of each of these Regulations, comparable best practice is to be expected.
Hand held devices will need to be considered	Because of the difficult conditions of use and the potential for poor equipment or job design, hand held devices will require explicit Human Factors consideration.
The guidance here will need to be part of a programme of work.	It is not possible to give assurance of usability by quoting a standard or even this document. A programme of work including risk management, specification, prototyping and test and evaluation will be needed. This is likely to form part of the Human Factors Integration Plan (HFIP).

Testing in the context of use will be needed.	Until there is much more detailed design guidance, it will be necessary to evaluate any proposed hand held device in representative conditions.
Novel input devices will need particular testing	Novel input devices such as speech input or pen input will need considerable testing with a range of users.
	Likely testing requirements can be identified.

This section presents the key criteria in summary form to aid device assessment. It is only a summary, and fuller guidance should be consulted if there is any doubt.

It is assumed that hand held devices will be considered as part of a Human Factors Integration Programme (HFIP), and that the checklists will be used in that context. Before using the checklists it is recommended that:

The order of checklists is considered the most effective sequence for device assessment once the context of use and task requirements are understood.

Individual checklists follow for each type of device, i.e.:

Review the candidate devices against the key criteria given here.

Check that representative users are able to perform each of the tasks required in representative conditions.