A diving regulator kit generally consists of the 5 following parts.
1. A first stage regulator
The first stage is connected to your cylinder and is literally the first stage in which air pressure is reduced as it travels from the cylinder to the diver.
You will find one or multiple HP and LP outputs at this stage.
The LP (low pressure) outputs are used to attach your primary second stage, your octopus and low pressure inflator hose.
The HP (high pressure) outputs are used to attach your SPG or a computer transmitter. Simply put they bypass the reduction of the first stage.
2. A primary second stage (or generally your second stage)
The second stage, your mouthpiece for breathing underwater, is connected to you first stage via a hose. Again, it is called the second stage because it reduces the pressure down to the ambient pressure allowing you to breathe safely. I’ll explain how this is done in a later post.
3. An alternate or back up second stage (or commonly an octopus)
In essence this nothing more than a back-up second stage, allowing you to help yourself in case your primary second stage fails, or share your tank with a diver in need of air supply. These are generally provided in bright yellow for easy location.
4. A Submersible pressure gauge (SPG)
This useful tool allows you to check up on your cylinder’s pressure level, or simply put it tells you how much air you have left.
Generally the SPG can be placed in a console along with a compass and a diving computer.
5. A low pressure inflator hose
This hose is connected to you BCD (buoyancy compensator device), allowing you to fill your BCD with air by the simple touch of a button.
When looking for a new setup, remember that a decent regulator set is an investment that will serve you for a long time. Make sure the first stage has the amount of dedicated outputs you require and keep in mind that you may want to expand your setup later on as you progress. (eg. an extra LP output is needed if you’d like to dive a dry suit.)