Voice Control is one of the most important accessibility features that the iPhone has for people with special needs, while also being a productivity tool that can increase how you use the device. It is, essentially, a way for you to use voice commands to control your iPhone and interact with it. This feature, however, did not jump over to the newest incarnation of the iPhone since Siri replaced it. Instead, there are only a small segment of devices that use it. Here is a look at how it works.
Voice Control is a relatively basic option, and similar to Siri, and allows for you to use voice commands to control basic functions like turning on a song or making a phone call. It does not, however, have the interactivity, personality, or ability to search in the way that Siri does. The command interaction is much the same and you can often do a seamless transition. In many of the Settings on the iPhone 4s it is still listed as Voice Control, so Siri can really be seen as an evolution of it. If people are discussing Voice Control, then the tips will likely still apply to Siri as they are often interchangeable in the discussion. Siri is a function that uses Voice Control, but for the purposes here Voice Control will refer simply to the voice command structure that was in place before Siri stabilized it. Voice Over, as an accessibility option, is also tied directly to Voice Control, yet functions somewhat differently.
The limited Voice Control feature is only available on a few models. The iPhone 3Gs and the iPhone 4 both have Voice Control, but the iPhone 4s replaced it with Siri. The third and fourth generations of the iPod Touch also have this feature. You had to have at least the iOS 3.1 on your device and you may not have the full range of possible languages until after the iOS 4.
To activate Voice Control you simply hold down the Home button until you get the blue Voice Over screen to pop up. You can then issue a voice command and it will begin to process on its own, which is much more hands free than Siri in a certain sense. The options, however, of what you can actually initiate are less than with Siri. You will have to make sure to talk clearly and without too dramatic of a voice presentation. Accents that are strong can cause some confusion. When you want to make a call to a person in your call list you may want to use their whole name if they have a short first name since it can get confused. You should also make sure not to pause for too long after you get the signaling beep that lets you know the Voice Control process has begun. Some people also have a problem with possessive language, so try to have as clear of a sentence as you can when issuing a command. Siri has been better at clearing up misunderstandings with the voice commands, but the more primitive Voice Control is not going to be able to differentiate quite as easily.
You have many options for language and you can change these in Settings. Once in Settings go to General, and the top of the third block of options. Go down to International, which is under Keyboard and above Accessibility. Here you will be able to set the language for Voice control, and a couple dozen options from here to choose from. This will include multiple regional options for the same language, such as three variants of Chinese.