Bone Conduction Microphone/earphone (non Vox)
This unit is a "passive" ( contact piezoelectric type ) sensor
based unit .It does not have the audio shaping electronics and VOX operation
that the more expensive battery operated Bone Conduction unit has .
It has an outboard PTT switch at the end of a separate 800mm cable that
can be attached to the finger by a loop of adjustable velcro . The moulded
silicone earphone unit has a vibration sensor in a "pimple" of
silicone rubber that rests against the hard bony surface of the ear canal ,
this picks up the internal vibrations from speech. There is a small sealed
unit near the radio plug that contains a single transistor impedance conversion
stage to match the piezo microphone to the radios microphone impedance,
the power to run these components is derived from the PTT line of the
transceiver. The radio end of the other 800 mm cable is
terminated in a dual pin plug 3.5mm for the speaker and 2.5mm for the microphone
with a pin to pin distance of 10mm the PTT cable connects with the radio
cable near the two pin radio connector .
The earphone requires a good fit to the ear canal to be effective . It has good
received volume and clarity , the transmitted audio is not as high fidelity or
level as a good electret mic but is communications quality but does
require good clear speech and volume ( don't mumble!)
A good application of technique where by the natural high frequency response
of the piezo electric microphone is used to shape the received audio
( reduce the high amplitude bass and accentuate the low level treble)
required for understandable speech.
Price $80.00 inc gst plus postage
Pinfold Health Services Ltd.,1172 Arawa st,Rotorua 3201,New Zealand. ph +64-7-3488850 fax +64-7-3486555 pinfold@xtra.co.nz