[Icom] IC-2720H PTT circuit?

[Larry]

I can't address the 2720 directly, but every Icom rig I've had (and it's=20
been at least 10) all pull the PTT line to ground to key the rig. They=20
range from HT's to my 765.

73 - Larry W=D8NFU
larry_w@comcast.net


At 11:47 PM 8/4/2003 -0700, you wrote:

>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: K6PML@arrl.net
>
>
>
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