Many of the radios in the Clansman series of man portable transmitters are set up so that if you connect the headset/microphone directly to the radio it will transmit constantly and there is no way to switch the microphone on or off. It is unlikely that this would be very useful in operations, so a seperate switch is plugged in between the radio and the headset to allow the microphone to be switched on and off. This is known as the pressel switch and can be seen here in this diagram:

The switch itself is a small green box, with a cable at one side and a plug socket at the other:

The end of the cable has a standard Clansman socket on it, with a seven pin connector:

This end is attached to the corresponding socket on the radio:

The opposite end of the pressel switch is set up to allow the headset plug to be attached:

With the switch now wired in, all the operator needs to do is to depress the black rectangular button when he wishes to speak and release it when he wants to listen:

A large spring clip is attached to the side of the pressel switch to allow it to be secured to the operator’s clothing so it isn’t flopping around and getting in the way on the march:

My Clansman 350 is coming together really well now and all I am really missing is the harness to carry it and the surf unit to attach to the side: