[This post is part of our Designing Hardware for HD series. Be sure to check it out!]

It’s about time we deal with interfaces. Not the video ins and outs – I have already touched on that one. This time I want to discuss the interfaces that usually connect to a videophone product – and trust me, there are a bunch of options here.

Yes, I’m talking peripherals here – those pesky things your end-users will end up connecting to the videophone. They come in different shapes and sizes, and they fit different needs of the user.

Handset / Headset / Other Audio Peripherals

Essentially this means audio. How do you connect audio into the system, other than what the videophone comes with?

This can be a handset or a headset for a personal device, or a microphone pod for a room system. The interface you would choose to connect such devices will require additional work on your side – from adding microprocessors allowing such connectivity to writing software drivers to support new interfaces.

There are several options to explore for the audio interface:

• RJ11 is a telephone wire used to connect headsets to the phones in the wired world. It’s as simple as it gets. The main disadvantage here is that pushing back commands from the handset to the videophone will be difficult at best. Another issue to think about here is the requirement to convert from the analog input to a digital one on your videophone system itself.
• TRS connectors are the ones you can find on a laptop or a sound card for connecting a simple microphone or speaker. They are simple as hell, providing a large set of audio devices that can be plugged into them. I’d say they are mainly used for a headset. As with RJ11, you won’t be able to push back commands on them.
• USB – Still in the wired world, there is always the possibility of using a USB interface to connect an external handset or headset. USB has an added complexity of requiring a specialized driver for it, with a need to focus on the Audio device class for that driver. On the positive side, USB will allow you greater flexibility on the stuff you’ll be able to connect to it and will give you a good backchannel for commands.
• Bluetooth is similar to USB from my point of view, but gives an added bonus of being wireless. On the downside, you’ll need to think about power supply and battery charging of the end device. Done right, this will allow a myriad of Bluetooth headset devices designed for mobile handsets to be used for your videophone.
• WiFi is similar to Bluetooth in most respects, with the additional aspect of IP connectivity. This will require the least amount of hassle for drivers and will allow you to build a kick-ass device in terms of the flexibility you get on the control backchannel. As with Bluetooth, you will need to deal with power supply and battery charging.
• DECT – Some say DECT is a dying breed. While this might be true, I’d say it’s a proven technology for wireless voice transmission which you should look into if you’re in to a wireless headset/handset peripheral.

Storage devices

An external storage device is not something that would be interesting to all videophone products, but in some scenarios you might find them quite compelling.

The things you can do using a storage device are varied, but I’d say the following are the most common uses:

• Access multimedia files and use them in the context of a call
• Store recorded calls locally

The storage devices can either be connected or networked:

• Connected storage devices tend to be based on SD cards or external USB drives. They will require the end user to plug the device into your videophone in order to use it. It adds an aspect of control, portability and independence to the user.
• Networked – Home networking is one of the technologies that are being developed these days. You might want to enable connectivity over the local network to media servers or other storage devices that might exist.
  If you are interested in more information about this, I suggest you head on to DLNA – the consortium that deals with such technologies and standards.

Ethernet Switch

Some devices may enjoy the use of a built-in Ethernet switch. If you plan on having your device sitting near a PC on the desk of the end user, then such an internal switch will enable the user to have only a single Ethernet socket in the wall instead of requiring two of those – one for your videophone and the other for your PC.

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The above list is not an exhaustive one – it is just a set of examples for things I’ve seen people use.

Think about how you want users to interact with your product, and see if there are any additional connections that will make their lives easier.