Staying Connected - September 2010

Intuitive Designs for Cables and Connectors

One aspect of cable and connector design that is commonly overlooked is whether or not the intended user will intuitively know how to connect the device.  Ideally, when a user picks up a cable, he or she will know where and how it should be connected to the device.

Example of a Less Intuitive Design

Without careful inspection, it is difficult to know which side is up– an example of a less than optimal design

The USB “A” connector, the end that plugs into computers, is an example of a design that is not very intuitive.  Without careful inspection, it is difficult to know which way the connector should be inserted into the receptacle.  Users have a 50-50 chance of trying to insert the plug the wrong way.  In almost any situation, this ambiguity is undesirable.

All of the USB connector variants, “Mini-A,” “Mini-B,” Micro-AB,” and “Micro-B” suffer from the same problem.  Without careful inspection, a user is likely to insert it correctly only half of the time.  Because of its irregular shape, the connecting of a USB “B” connector is somewhat more intuitive.

Intuitive Interface

If an intuitive interface is desired, consideration should be given to this aspect of design at the very start of a project.  Answering a few simple questions may help lead to an intuitive and easy-to-use design:

  • How will the user know which end of the cable is to be plugged into the device?
  • If there is more than one receptacle, how will the user know into which receptacle it should be plugged?
  • How can the user determine the proper orientation to mate the connector to the receptacle?
  • If there is a latching mechanism, how will the user know what is the proper way to connect or disconnect the cable from the device?
  • Is the connector large enough to be easily handled by the intended user?
  • If forced, is there a mechanism to protect the plug and receptacle from likely damage?

Device End of the Cable

For some medical cable assemblies, it is obvious which end is the device end and which end is the patient end.  As an example, EKG cables have multiple electrode connections on the distal end and it is relatively apparent that end is the patient end.

Example of color-coded device
receptacle and color-coded strain
relief on cable – mating is obvious

On the other hand, many cables are designed to connect between two devices and it is often not as obvious which end is to be connected to the primary device and which end connects to the secondary device.

Device Receptacle

Besides mechanical and electrical performance requirements, the location and configuration of the device receptacle is often a key element in the user knowing how and where to connect a cable assembly.  If multiple cables will be connected to the device, extra consideration should be given to differentiate the receptacles, making the connection intuitive.  Ideally, any markings should be large enough for those with less than perfect eyesight to see them even in poor lighting conditions.

Connector Orientation

Example of connector with color-coded
shell and angled strain relief making
orientation obvious to the user

Connection to device is intuitive due to
color coding of both the receptacle and
strain relief.  The connector angle and size facilitates easy and correct insertion

Connector orientation can be problematic if the user does not know how to plug the cable into the receptacle so that the pins and sockets engage properly.  The plug or receptacle can be damaged if the connector is forced, rotated while the pins and sockets are engaged or inserted at an improper angle.

A common way to prevent damage to either the plug or receptacle is to design the pair so that plastic on both sides engages and guides mating well before pins engage with sockets.

Hard plastic surfaces mate and guide pins and sockets to engage properly and without the possibility of damage

Example of a recessed keyway which
prevents a cable without this specific
keyway size and shape from being
plugged in

Keyways are also commonly used to assist in proper mating.  Keyways can also be used to prevent a connector from being plugged into the wrong receptacle.  Keyways should be large and strong enough to prevent either misalignment or damage that would make the keyway ineffective.  An effective keying mechanism should make the connection nearly foolproof.

”D-shape” facilitates proper orientation.
Users will typically place their thumb
on the flat surface which may help
orientate the connector.

Connector Size

As medical electronics become smaller and smaller, the tendency is to specify smaller connectors.  Consideration should be given to connector size so that any likely user will not find it difficult to handle the connector.  This becomes a more significant design element when the intended user has reduced dexterity or when the connection may need to be made quickly as in an emergency situation.

Connector Shape

A uniquely shaped connector and receptacle can make it apparent to the user where the plug is inserted and can also prevent misconnection.  Besides misconnection, a uniquely shaped connector can prevent all but the intended cable from being used.

The shape of the connector can also make mating intuitive.  An ideal situation is that when a user picks up a connector, the proper orientation is obvious.  One way to achieve this is to use a “D” shaped connector instead of a round or rectangular connector.  Even without markings or labels, it can be obvious that the user’s thumb fits the flat surface of the “D” which orients the connector for proper insertion.

Examples of color coded
overmolded strain reliefs


One way to achieve an intuitive cable design that is easy to use is to use color-coding on both the cable and device.  This is especially helpful when the device has more than one receptacle.  To achieve color designations on the connector, it is common to overmold the strain relief in a color that will match the color indicators on the receptacle.  If a slip-on boot is desired, many off-the-shelf connectors can be ordered with colored strain reliefs.  In addition, the pin insulator can be color coded to the device receptacle.


Often markings on the connector are employed to help users understand how the connector is mated to the device.  When markings are used, care should be taken to ensure that they are large enough to be effective.  If the design calls for a custom connector, raised markings can be molded into the connector which provides both a visual and tactile reference. 

Large raised arrow helps user orient
connector for proper insertion

Example of pad-printed arrow
to assist in connector insertion

Another option for marking is printing or applying a permanent label directly onto the connector.  The materials and shape of most connectors limit printing to simple graphics in a single color.  If multiple colors or complex graphics are desired, a permanent and durable label can be affixed to the connector.  In either case, printing or graphics should be easily read or recognized to be effective.


When designing a medical interconnect device (a cable assembly or a connector), consideration should be given to making the intended connection as intuitive to use as possible.  If the design of a medical connector or cable is intuitive, the intended user should be able to connect or disconnect with little or no thought and without the opportunity to damage the device or connector.

The Affinity Engineering Team can help you design an interface that is intuitive, robust and cost effective.   Take advantage of our experience and expertise and help to complete your project on-time by making us part of your team.

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Meet Bob Frank – Affinity Director of Engineering

Mary Phillipp and Bob Frank
worked together before founding
Affinity Medical in 1997

The atmosphere at Affinity Medical is highly charged and a lot of that can be attributed to Bob Frank, Affinity’s Director of Engineering.  Bob’s imposing stature (he’s 6’6” tall), unmistakable laugh and genuine enthusiasm help keep the energy level at Affinity very high.

Bob has spent his entire professional career, spanning nearly 30 years, in the medical interconnect industry.  After graduating from high school, Bob joined Tronomed, a large medical cable manufacturer, as a draftsman.  Bob quickly learned what went into designing a high quality medical cable.  Because of his enthusiasm he quickly moved from the drawing board into sales.  Bob eventually led the sales team at Tronomed, directing both inside and outside sales.

At Tronomed, Bob worked with Mary Phillipp, the President of the company.  They established a strong professional relationship and a long term friendship.  When Tronomed was acquired and moved, Bob jumped at the opportunity to join with Mary to found Affinity Medical.

Bob shares his experience
and expertise with
Affinity Engineering
Supervisor, Matt Pathmajeyan

While in its “infancy,” Affinity landed a major OEM account.  Bob and his wife, Joanne, worked alongside Mary Phillipp, her family and other team members for long hours doing whatever it took to get Affinity up-to-speed on the project.  Bob recalled the time he and Dave Johnson (Mary’s husband) were running molding machines almost around the clock. “We’d run parts until we were too tired to continue, retreat to our cars and catch a couple of hours of sleep, wake up and start the process all over again!  It was worth it.  We shipped on time and made our first large OEM customer very happy.”

Bob’s technical knowledge and high regard within the industry landed him a spot on the committee that established the ANSI/AAMI EC53 standard.  EC53 is the only standard to specifically address the technical requirements for medical cable assemblies and leadwires. 

Thirteen years later,  Bob is still as enthusiastic about Affinity.  He willingly shares his positive attitude and extensive experience with the Affinity team.  Bob can be quoted as saying, “We all work hard at Affinity, but we also have a lot of fun.”

“Bob has a vast knowledge of every aspect of medical cable design and manufacturing.  He is an extremely helpful resource to not only our customers but everyone at Affinity,” said Hank Mancini, Affinity Business Development Manager.  “Bob is unique in that he has both a great technical background, but also years of experience on the sales side.”

As a member of the Affinity
management team, Bob updates
the production team on
new products being
released to production

When asked what he enjoys most about his position at Affinity, Bob said, “I enjoy and value the relationships I have developed over the years with customers, suppliers and other employees here at Affinity.  It is great to be able to do business and work with people that I respect and consider friends.”

Besides work, Bob is an avid golfer with a single-digit handicap.  He also is a Formula 1 race fan.  He says, “I love engineering, technology and competition, which are all exhibited at the highest level by Formula 1 racing.”

Bob and his wife love to travel and especially enjoy visiting sites of historical significance.  This past summer, they vacationed in Europe visiting Prague, Normandy, Mont St. Michel and Bruges.  Bob and his wife also enjoy wine and took time to visit several of the Champagne houses in Reims, France.

During the winter, when not working at Affinity, Bob enjoys snowboarding at Mammoth Mountain in California or other ski areas in the west.

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The Affinity Blog

Photo from Cindy’s blog on
Peach Days in Hurricane Utah

About once a week, and occasionally more often, Affinity team members share something of importance or interest to themselves with the world by posting an article on the Affinity Blog.

The Affinity Blog can be accessed on Affinity’s web site,  The link to our Blog is in the upper right-hand corner.  It can also be directly accessed by entering the URL:  Either way, this is an area where Affinity team members can let others know what they think or what they are thinking about!

Recent blogs have included:

If you have not done so already, check out the Affinity blog.  We think that you’ll find it interesting and it will give you an additional “view” of Affinity team members.

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Announcements & Information

October Trivia

October is the eighth month in the old Roman calendar which is how the month got its name.  “Octo” in Latin means eight.  October retained its name even after July and August were added to the calendar and named after Julius and Augustus Caesar.

Children and adults enjoy
dressing up for Halloween

Both Cyprus and Nigeria celebrate Independence Day on October 1st, while St. Vincent & the Grenadines and Turkmenistan both celebrate independence on October 27th.

Most popular among children is the last day of October, Halloween!

Suzann Sitka, Cesar Jara and Candy Golding
- the Affinity Customer Care Team

Affinity Customer Care -
Hours of Operation

Affinity Medical Technologies customer care specialists are available to assist you from 7:00 A.M. until 4:00 P.M. Pacific time, except holidays.

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