Service Manual

Page 6.18
6 ~ CIRCUIT DIAGRAMS
Headset socket 3.5mm - loudspeaker disconnected when jack inserted
Environmental:
Operating temperature range –20°C to +55°C
Storage temperature range –40°C to +80°C
Figure 3 Lapel Speaker Microphone Circuit
OPERATION
Ancillary Type
R3 defines the ancillary as a Lapel Speaker / Microphone.
Microphone
The microphone connects to the radio via the tip of the 2,5mm stereo jack (J1) and is powered via the ring
and sleeve of the 3.5mm stereo jack (J2) on the cord assembly.
When the Lapel Speaker / Microphone is connected to the radio, the radio’s microphone is switched out of
circuit.
Operation of the PTT switch brings into circuit the Electret microphone, which is powered from a rectified
and filtered DC supply from the radio. R5 is used to generate a PTT interrupt to the radio.
Speech is superimposed onto this voltage on using the microphone with the PTT switch pressed.
Loudspeaker
The loudspeaker connects to the radio via the ring and sleeve of the 2.5mm stereo jack (J1) on the cord
assembly.
When the Lapel Speaker / Microphone is connected to the radio, receive audio is routed to the ancillary
loudspeaker and not to the radio’s.
The Lapel Speaker / Microphone supports the use of a remote headset.