Decoding the Number Lock

Task analysis is a common practice which can be adopted by anybody who is looking to design, delegate or deploy any idea or product. Some of the purpose served by it are as follows

• To write down the Standard Operating Procedure for any task.
• To identify the users that are excluded from performing the task.
• To perform the Failure Mode effects analysis.
• To help students with learning disabilities to learn in a classroom setting.

The object for the task analysis can be seen on the left. A number lock with a single rotatory dial. The intended purpose of this lock is to selectively provide the access of an area enclosed with 5 sides and the sixth side has a door

mechanism with a hoop. The shackle passes through the hoop of the door and through the second hoop which can be on the adjacent wall or on the other half of the door thereby in the condition that the lock is put, there is no access to the area behind the door/s.

The task of using the Number lock can be broken into the following steps-

• Legally purchase a number lock.
• Identify the door on which the lock needs to be put.
• Take the lock out of the packaging.
• Look for the opening combination, usually written on the packaging.
• Memorize the combination/keep a copy.
• Make sure the hoops are big enough that the shackle can pass through them.
• Put the lock such that the Dial is facing outward and the vertical orientation is such that the shackle is upside and the rotatory dial is downside.
• Press the shackle such that it goes inside the hole in the lock.
• The click of the locking latch signifies the locking.
• To open- rotate the dial anti-clock wise till the first number is reached.
• Now rotate the dial clock wise such that it passes through the first number and reaches the second number.
• Rotate it anti-clock wise to reach the third number.
• Pull the latch out.

The Task Analysis done above would help us in identifying the excluded users. The User capabilities can be classified broadly into 7 categories. And any step that requires any of these would render this device useless for a user without that particular capability.

• Vision- Barring a few steps (1, 9, 13) this task has a large visual component. This lock in its present form factor would be difficult/impossible to operate for user with visual impairment.
  - A lock with a key could solve the problem of matching the numbers or may be if the instructions and the number on the dial are written in braille, then this lock could be operated by a visually impaired user. Trade off- the size of the lock would increase to accommodate the braille characters. Since engraving the braille characters might require machining that might add to the cost.
• Locomotion- None of the steps involve body movements like bending, climbing, standing, sitting hence this lock is operable by a user with locomotion disability.
• Auditory- Despite of having a sound of click the step 9 can be skipped in lieu of tugging at the shackle. Hence this lock is operable by a user with hearing impairment.
• Communication- Step 1 does require communication however strictly if just the operation of the lock is concerned, that starts from Step 2. There after there is no need to communicate with anyone else and hence a user with disability to communicate can operate the lock.
• Cognitive- Retrieving from memory or reading out from a slip of paper both requires cognition. Also, matching the number on the dial to the number on the code is a cognitive process. This lock is useless for a user with cognitive disability.
  -  If however the system changes from what he knows or what he has to what he is, it becomes useful to a cognitively impaired user. The solution could be fingerprint, retina scan etc. Trade Off- Any kind of scanning is an electronic process which would require a battery and a circuit board adding both to the cost and to size of the lock.
• Reach and Stretch- Every step after Step 7 requires the user to extend his arms to reach to the lock and hence this lock in its present form factor would be difficult/impossible to operate for user with limited Reach and Stretch impairment.
• If the lock could be made smart i.e. if it could be operated by using remote or cell phone then that could counter the above limitation of the users. Trade Off- There are currently a few locks that are smart and use an RF ID, these are however installed in the door and are not portable.
• Dexterity- Prying the lock out of its packaging involves strength of fingers and hands, locking involves squeezing and the unlocking involves rotating the dial. A user with dexterity limitations would not be able to operate the lock.
• A modified lock which does not have a dial to rotate but a simple key could be a potential solution. Or a system in which the cylinders inside the lock does not align by rotating the key but by pushing of a button. Trade Off- In the existing system the key might get lost, also putting the key inside the hole might be challenging for a user with dexterity limitation.

Usability Evaluation of a device is done to engage the users and find out the specificity of the operations. After the task analysis has been done, the usability evaluation can be employed to validate whether the steps are elementary or there still exists a discrepancy between the intent of the designer and the understanding of the user.

1. Users were given the locks and were told- “Please find the opening combination of the lock”.

• It is important that the users are able to locate the opening combination of the lock hence if they are accidentally throwing away the small paper containing the combination or tearing it during opening the package then it is a problem that needs attention.

1. Users were given the combination and were told- “Please memorise the combination in 10 minutes”.

• If the users are having problem memorizing the combination then 3 turns might not be a practical option, we might be trading off efficiency for security. On the flip side if the users could do that easily then this might serve as a good background for shifting to more number of turns.

1. Users were given the lock and were told- “Please put on the lock”.

• If the users are not orienting the lock correctly i.e. the dial facing the front and the shackle on top then we might want to design it such a way that it can’t be put the wrong way. Another option could be to describe the way to put the lock the right way in the instructions of use.

1. Users were given the combination and were told- “Please open the lock”.

• If the users are not able to enter the numbers correctly the friction in the dial needs to be increased or its diameter so that the numbers are slightly further to each other and the user is not confused.

1. Users were made to stand beside another user and were told- “Please try and decipher the combination”.

• If the user could easily see the correct combination then this raises serious questions about the effectiveness of the lock and we might need to address it by adding a flap or some other mechanism. If, however the users are not able to guess it this would increase the user confidence on the product.

Shown below is the visual data of the UK users (figures of 1997) excluded on the basis of the capabilities required to operate the Lock.

The above study helped us design the Standard Operating Procedure, determine the users excluded and judge the effectiveness of the Stand Operating Procedure. Also the excluded users study provided the easiest product development. Such products which are minor tweaking of a previous product are called as Platform products and are the safest products to launch in the market.