[App_rpt-users] Parallel Printer Port Question

[Stephen Rodgers]

On 11/06/2010 06:21 PM, Randy wrote:
> I have the Parallel Port setup and working fine on my system for
> Cor and PTT
> The only issue I have is if the computer shuts down for some 
> reason, Lost of power ect the radio keys up and stays keyed
> intill I toggle the ptt on and off using the F command in the Radio
> Tune menu. Is there a work around for this.
> 
>                                                          Randy
> 
> 
> 
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It's not completely clear from your message what the issue is.

When you shut your PC off, the parallel port pins will tend to go to ground. If you use low true keying, this will keep
the transmitter keyed.

To correct this problem, put an NPN transistor (2N2222 or 2N4401) with a 1K-2.2K resistor from the base to the PTT pin
on the parallel port and change the config to using high true keying. Connect the emitter of the NPN transistor to
ground and the collector to the ptt line of the radio.

When the PC is turned off or reset, the parallel port output will want to go low, turning the NPN transistor off. The
collector of the NPN transistor will then go high, unkeying the rig. When PTT is asseted high by app_rpt, this will
turn on the NPN transistor, and PTT connected from the collector to the rig will be forced low.

Steve
WA6ZFT




Steve
WA6ZFT