Simon Rockman continues his look at mobile phone form factors with an explanation of clamshells


About ten years ago there were two types of phones that dominated the shelves of your local Carphone Warehouse: bars and clams, in the UK we were fairly evenly split between who liked what, with Motorola and Samsung dominating sales of clams and Nokia with bar phones. Then sliders came along and Clams became “old fashioned” in the minds of  the people who bought phones for the networks and it became very hard to sell clams in quantity.

This is a real problem for the fuss free phone market as most of the best easy to use and big button phones such as the Doro 410 are clamshells.  The clamshell has a huge number of advantages in an easy to use mobile phone.  The most obvious is space, because an open clamshell is about 50% taller than a bar phone you’ve got room for the big buttons, with good spacing and a big display without having a giant phone.  This alone would be a major reason for choosing a clam as the best  option with easy to use mobiles but there are many more reasons. I particularly like having a mechanical action for answering and hanging up a call. It can be a little unnerving having a moment of indecisiveness as the phone rings and you try to figure out what to press. There is something a little Star-Trek satisfying about snaping a phone open. At the other end of the call it’s even more important. Shutting a phone to end the call means it’s definitely hung up.

The Dro 410 has clear easy to press buttons and a bright screen

The Doro 410 shows how a clam allows space for big buttons, with good spacing, and a big screen

A downside of covering up all the keys is that you can’t “busy” a call without opening it and answering. On some phones the volume key on the side doubles up to serve this function and you can often set a phone to not answer when you open it but to need you to press a button. To my mind this defeats the purpose.

Some people argue that opening and closing a phone is more physically demanding than pressing a button, and this is true, but only slightly so particularly with phones like the Doro and Geemarc that are pretty easy to open. There have been phones with springs top open them but these can be harder to shut and one from Samsung, the P510 which has a motorised opeing and closing mechanism.

An important aspect of the clam design is where the weight is in the phone. It needs to be heavily biased towards the based of the phone.  Ideally the centre of gravity of the phone should be under the 5 key. This stops it from tumbling out of your hand when you open it.

One aspect I like with a clam is that it covers the keys, not because it prevents in-pocket dialling but because if I’ve bought a phone that caters for my worsening vision I don’t particularly want to advertise the fact.  My myopic secret can stay that way.

For really non-techie users there is an added bonus that they can’t see the screen when it’s shut. You might think that this was A Bad Thing, but some people think that if the screen is off the phone is off and so won’t receive incoming calls. The concept of standby can be hard to grasp.

The audio can be better in a clamshell, one thing sounds likes is space.  With the extra room afforded to the speaker in the top of a clam there is more room for resonance and for a bigger speaker. This means clearer as well as louder sound.

Clamshell phones are quite a bit more expensive to make than bar phones. They need two printed circuit boards – although some will use the same one as a bar phone for the bottom half and as the screen is the most expensive part of a phone it adds a lot to the bill of materials if you have an external screen to  show caller identity. Currently no phones aimed at the easy to use phone market do this. As you might imagine assembling a clamshell is much more labour intensive than a bar phone.