[Elecraft] [acom-list] Re: Elecraft K3 and ACOM 2000A

[Lynn W. Taylor, WB6UUT]

There is the formal standard, and there is the defacto standard.

The formal standard says +3v for 1, -3v for 0, and that less than 3v is 
undefined.

The common driver chips (1488 and 1489) worked just fine with TTL levels 
-- 5v being above +3, and 0v being close enough to -3v.

I've never seen anything that required -3v for logic zero.

-- Lynn

On 9/15/2014 6:59 AM, Don Wilhelm wrote:
> David,
>
> That is true the specification says that condition will not cause 
> damage to compliant drivers and receivers, but if two drivers are 
> placed on an RS-232 signal line, they will *not* work together and 
> will result in corrupt data (assuming they are on the TXD or RXD 
> signal lines).
>
> You are correct that damage may occur to non-compliant (but 
> compatible) drivers and receivers.  The PC serial cards, USB to serial 
> adapters, and most ham gear do not implement compliant RS-232 interfaces.
>
> 73,
> Don W3FPR