Combination Devices

I

’m in two minds about a combination device – that is, a device that integrates a cell ‘phone with a personal digital assistant.

On the face of it and for many users, combining a mobile with a PDA makes perfect sense. Rather than using the PDA to find a ‘phone number and then entering this into your ‘phone, you can simply dial it. Or rather than having to connect your PDA with a ‘phone, then connect the ‘phone to the Internet, you can do it from the one device.

It also means that you only carry one unit with you rather than two, and although many combination devices are quite large in comparison to their single function cousins, they’re often smaller than carrying both devices at once.

The SPV E200 and Palm Tungsten W are two examples of combination devices.

However, the advent of Bluetooth radio enabled devices has certainly simplified the above tasks. Pairing your Bluetooth-enabled PDA with a Bluetooth-enabled ‘phone means that you can dial numbers and check email direct from the PDA without needing line of sight.

However, the disadvantage is that using the Bluetooth radio consumes power. The power consumption is much reduced when two paired devices are within range of one another, but when they are separated the power consumption is dramatically increased (as the devices search for other Bluetooth-enabled units). If you disable the Bluetooth radio on either device, you have to remember to re-activate it before using it.

However, there are also significant and material disadvantages associated with having a combination device. Although in aggregate, a combination device is smaller than two individual devices, it may in isolation be quite heavy and bulky. This may mean that whereas before, you could secrete your ‘phone in a jacket pocket and your PDA in a shirt pocket, the combination device doesn’t fit in either. Another difficulty that must be overcome by the designer is that of making the PDA functionality accessible to the user whilst making a voice call. One of the key advantages of having separate devices is that you are able to access your data when using the ‘phone and if you are unable to continue to do this with a combination device, this is a major drawback. Again, the use of Bluetooth radio and wireless headsets has improved things is the device has a Bluetooth radio. Once a user is over the initial discomfort of wearing a headset (the sensation is that you're talking to thin air) these typically work well.

Another disadvantage is that you are levying a heavier drain on the battery. Admittedly, for some PDAs the addition of the GSM / GPRS radio is not going to make much difference to battery longevity, but for other devices it makes a big impact.