Sender

The Sender section of the earplug contains a 1 khz Sine wave Tone Generator, a Pink Noise Generator and an Internal Microphone any of which can be selected to send signals down a balanced audio cable. The signal sent can be mic level (-40dB), an intermediate level of -20dB or line level (0dB) using the level switch.

To select Tone or Pink Noise as the generated test signal, open the battery door and pull the battery out (there’s no need to disconnect it). Four DIP Switches will be revealed and DIP 3 will select between Tone and Pink Noise.

The Mode Switch selects between a test signal (sig) and the internal microphone (mic) and the Multi Switch operates differently depending on the mode selected.

Imagine the situation...

You are at the end of a long microphone cable which apparently doesn't work.

You connect the suspect cable to the earplug Sender socket.

If there is a phantom power supply on the cable, before the earplug is even switched on, you can get an immediate indication if the cable is OK as the Phantom power led's will light up.

If you only see one led illuminated, the cable is one legged and if neither of the leds illuminates then either the phantom power switch on the sound desk isn't switched on or the cable is earth lifted (or of course you are connected to the wrong cable!)

If you select SIG on the mode switch and "0" on the Level Switch, someone at the other end of the cable can listen directly to the signal, (using another earplug!) or they can listen through a Mic channel on the sound desk if you select "-40"on the Level switch. If you need to identify the tone you are sending you can press the Multiswitch which will cut the tone momentarily.

By selecting Mic on the Mode switch you can talk down the cable. To prevent embarrassment (as in " that bloke at the other end doesn't know what he's doing") you can only be heard when the Multiswitch is pressed. More on this useful feature in communications.

Another use for the Osc mode is for the multiskilled(?) single-cameraman. He is now able to record test tone with the colour bars at the beginning of the tape, without the services of a soundman

The Pink Noise signal (selectable using DIP 3 under the battery door) is useful for setup and testing of loudspeaker systems, as it is less painful to listen to at high levels, and will drive all of the speakers in a multi driver cabinet  or system.