TMC Radio SRP 9100, Service Manual

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A1
Page
6.17
6 ~ CIRCUIT DIAGRAMS
TNM-M-E-0012 Issue 1.23
APPENDIX B - ACCESSORIES
Lapel Speaker Microphone
Figure 2 Lapel Speaker 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.
Specification
Maximum circuit current 10mA
Type Electret
Impedance
2k
Ω
(nominal)
Sensitivity –64dB ±4dB at 1kHz (0dB = 1V / µbar).
Sensitivity variation relative to 1kHz over
frequency range Less than +10dB, –2dB, 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 active PTT
voltage Less than 5ms to reach 95% of the nominal PTT
DC voltage established time for PTT release 50ms ±20% to reach 95% of the nominal PTT release
voltage
Loudspeaker
Impedance
16
Ω
±2
Ω
Power rating 0.3W nominal, 0.5W maximum