[Icom] IC-2720H PTT circuit?

Tue, 5 Aug 2003 01:53:20 -0400

Pin 4 to pin 7 will key the rig.

     William J. Diamond
    Rogers, Arkansas USA
   [email protected]

   Ham Radio Operator WR�T
Please Visit My Icom Radio Page At
http://pages.sbcglobal.net/wjdiamond/index.html

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Paul Lufkin
Sent: Tuesday, August 05, 2003 2:47 AM
To: [email protected]
Subject: [Icom] IC-2720H PTT circuit?

My apologies if this question has been asked before...

I'd like to use a stereo headset and microphone combo with an ICOM IC-2720H
when I set up as a base station during emergency/disaster operations.

I've already made an adapter to join the audio outputs into a stereo plug
for the headphones.

Does anyone know how to activate the PTT at the microphone jack?  Ground it?
Pull it high?  Connect it to something else?

Pin-out at the microphone connector is:

 1 +8 V DC output (Max. 10 mA)
 2 Channel up/down
 3 8 V control IN
 4 PTT
 5 GND (microphone ground)
 6 MIC (microphone input)
 7 GND
 8 Data IN

I'm assuming that the mike should be connected to the mike input at all time
and activating PTT also enables the microphone input, but if you know
otherwise, please correct me.

(BTW, given the previous discussion about getting service manuals, I haven't
tried that route yet...)

I understand that the "smart" speaker-mikes like the HM-133 by-pass the
wired PTT circuit and use a digital scheme, but the simpler HM-118 does use
it.

As an alternative, does anyone have the schematic for a HM-118?

Thanks in advance for your assistance.

Paul Lufkin, K6PML   Email: [email protected]

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