Simoco SRP8000 SERIES, Service Manual

Page: 73 / 94

TP0332/2 B.1
SRP8000 SERIES VHF/UHF PORTABLE RADIO
APPENDIX B - LAPEL SPEAKER / MICROPHONE
Figure B.1 Lapel Loudspeaker / Microphone
INTRODUCTION
The lapel loudspeaker / microphone is a robust, lightweight, unit with an integral press-to-talk (PTT)
switch and a headset socket. The unit connects to the portable radio via a 1,5m ‘curly’ cable with a
2,5mm (J1) and 3,5mm (J2) stereo jack plugs mounted in a single moulding.
Terminology
In the following text, switch states and jack connections are defined as follows:
SPECIFICATION
Microphone
Maximum circuit current 10mA.
Type Electret.
Impedance 2k
Ω
(nominal).
Sensitivity –64dB ±4dB at 1kHz (0dB = 1V / µbar).
Sensitivity variation relative to 1kHz over Less than +10dB, –2dB.
frequency range 300 Hz to 4kHz.
PTT switch
Push to transmit.
DC voltage overshoot during switching periods Within 2% of nominal voltage.
PTT ‘click’ suppress circuit:
DC voltage establishment time for Less than 5ms to reach 95% of the nominal PTT
active PTT voltage.
DC voltage established time for PTT 50ms ±20% to reach 95% of the nominal PTT
release release voltage.
Sleeve
Ring
Tip
Switch ‘closed’
Switch ‘open’