GP300 Speaker/Mic - DC blocking capacitor?

[M3SGC]

I have a circuit diagram for a GP300 Speaker/Mic assembly but there is no DC blocking capacitor. Question;
Does the GP300 use an electret condenser mic insert and if so is the "blocking cap" in the radio itself?

[Al]

Yes, the mic element in both the remote speaker mic and the radio's internal mic are electret. The DC block is inside the radio at the input to the first audio amp(C427, .018 uF). The mic side of the capacitor has what amounts to 2.2k ohm resistors to +5V for biasing both the internal mic and the remote speaker mic.

[M3SGC]

Thanks Al.