Thursday, 6 February 2014

Choosing the right earpiece and PTT for your radio. 1 wire, 2 wire or 3 wire?

Choosing the correct radio headset is important. As professionals we seek perfection in our work and with the tools of our trade.  Too often headsets are either supplied as standard issue or often get overlooked and suddenly become a matter of urgency.

It is not the technical specifications I get asked for most all but rather "What is the difference between all the  models"?

The first man difference is the type of Earpiece or Ear speaker. Te three most common choices are below: 

C or G Ear Hanger
D Shell Ear Speaker
Acoustic Tube Earpiece
The C style or G style Ear Hanger has some adjustment and a speaker that fits in the ea.
The D style fits over the ear lobe.
The Acoustic tube fits in the ear and no spill is heard by a third party.
Other styles exist from very simple to covert wireless earpieces.

Once you have chosen the listen device the 2 other important items on your headset will be the microphone and the PTT (Press to Talk) switch that will operate the talk mode on the radio for an external mic. This is the point at which you will determine if you require a 1 wire, 2 wire or 3 wire headset.

Just before we read on to the I have a USEFUL TIP to offer .  If your control operator calls through to say  your voice sound miles away try operating the PTT switch n you headset.  Now simultaneously scratch the mic on your headset. If your operator cannot hear the headset mic being scratched now try scratching the radio's on board mic. If they can here this there is a fault, poor connector contact / broken PTT.  On most radios if you press the side PTT switch with a headset plugged in the radio's on board mic will be operated.

1 Wire Radio Accessory

Effectively a continuous cable travels up from the Radio connector to the earpiece. 
A single wire goes up from the connector to the  PTT ( Press To Talk) unit which also contains a encapsulated mic. A cable then continues on to the earpiece unit. A 1 wire accessory has the least amount of cable. The PTT unit is worn on the lapel or at lapel height. There is not usually enough cable on the earpiece cable section to wear the PTT unit in your sleeve.

2 Wire Radio Accessory
With a 2 wire accessory there is a separate cable for the PTT/Mic unit and earpiece. This enables the PTT/Mic unit to be worn down the sleeve.
There may be 2 cables exiting from the radio connector or there may be short run of single cable to a splitter unit.  The mic cable and the earpiece cable then exit from this

3 Wire Radio Accessory
In a 3 wire accessory the 3 constituent parts, Earpiece, mic and PTT unit each have their own cable giving the most flexible options for surveillance work. 3 Wire kits may also be known as a harness.  They may also include an induction neck loop for a covert wireless earpiece.

Choice of Mic.
Most encapsulated microphones are small eletret capsules that are held behind a small hole in the PTT unit.  It is worth locating this small pin hole opening as once you know where it is you will never accidentally cover it with you finger. I would also recommend familiarising yourself with the working properties of your microphone.

There will be an optimum distance and an optimum voice level at which your transmission will sound clearest to your radio controller.  Different microphones have different response coverages (polar diagrams for the techies).  Try establishing these properties with the help of a colleague and a second radio.  If you have Tetra radio you can use your radios in DMO mode to test with. Once you have established these properties try the same position from behind the mic and to the left and to the right of the mic as well.

Once you have established  these properties you have a bench mark to compare within different situations. Turn up the TV or CD player in the background and now compare how the microphone performs with loud background noise.  Is it clearer to the listener if you speak more closely, more quietly or shout into it?

Choice of PTT Unit
There are many different styles of PTT unit.

ABOVE: The most common style PTT units is shown above.

LEFT: The square front facing PTT unit to ideal for use with gloves or clipping to protective body armor. 

RIGHT Torpedo switch used on 3 wire kits worn down the sleeve .

I have a rule of thumb, (it is a guideline only, it has no technical or legal merit) that if it becomes noisy and you need to turn the volume right up to hear your radio then you probably have the wrong type of headset for noise applications.


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