[GreenKeys] DTE & DCE on a modem

[Bob McConnell]

Larry Tighe wrote:
> Howdy Folks,
> 
> Got my hands on some Black Box CL050A modems.  Planning to try keying a 
> HV transistor with the RS-232 outputs.  They are designed to key a 
> current loop which they supply 18 volts to.
> 
> Can anyone tell me what DCE and DTE means?  There are dip switches 
> that'll have to be set up....
> 

Larry,

Is that a true RS-232 output? If it is, it is a polar output that 
switches between +/- 18 volts. The voltage spec for the RS-232 series 
has always been that valid outputs are between 3 and 24 V, positive or 
negative. Anything less than 3 V is undefined and to be considered below 
the hysteresis threshold. Yes, that is a holdover from the days of glass 
enclosed vacuum tubes.

Bob McConnell
N2SPP