Yoga Headset Vox unit:
The EM-800 will enable hands-free operation on most commercial and amateur radio handheld transceivers (Yeasu,icom ,standard,etc) that have the facility to connect an external mic via a 2.5 mm mono jack and an external speaker via a 3.5mm mono jack .
This is a headset with an integral boom mounted unidirectional electret microphone and an impedance of 2.2k ohm. The earphone has a nominal impedance of 32 ohms and an audio level of 90db SPL at 1 khz and 1mW. The control electronics is in a small match box sized unit that is powered by a single 1.5v "AAA" battery. The unit has a high, low sensitivity and off (PTT) mode. The speaker plug is a 3.5mm mono jack and the microphone a 2.5mm mono jack ,The earphone volume is controlled by the volume control of the transceiver.
The 3.5mm speaker plug is inserted into the transceiver, while the 2.5mm mic plug goes into the external mic socket. The unit is placed on the head and the earphone position and mic position adjusted for comfort. The mic needs to be about 1.5-3.00 cm away from the mouth. The unit is switched on and the vox sensitivity adjusted to cater for the ambient noise level of the immediate surroundings, ie High (-93db) or Low (-83) db sensitivity. There is an acoustic difference of about 10 dB between the mic sensitivity settings. The users voice level is modified to allow the radio to automatically transmit. There is a built in delay of about 0.8 seconds to allow the radio to stay in transmit mode in between words, any delay of over 0.8 seconds and the radio will drop back to receive. The mic jack is switched by an NPN transistor to earth (the emitter is connected to earth) The resistance across the 2.5mm mic jack goes from meg ohms on "receive" to about 3k ohms on "transmit".
If you wish, the unit may be operated in manual mode. On the same side of the control box as the sensitivity control can be found the small PTT (push to talk) switch. This switch is active at all times even when the unit is turned off. (There will be no current drain when the unit is actually turned off)
Price NZ $30 plus postage plus gst (US $17.00)
Pinfold Health Services Ltd,1172 Arawa st,Rotorua 3201,New Zealand. ph +64-7-3488850 fax +64-7-3486555 firstname.lastname@example.org
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