🚀 go-pugleaf

In article <5521602MR@MSU>, Mark Rosenberg <21602MR@MSU.BITNET> indicates 
that he would like video from a Mac II to be displayed identically on two 
monitors.  

The box that he wants is called a "video distribution amplifier", known in 
video as a DA but I won't call it a DA in THIS newsgroup.  A distribution 
amplifier has a single set of video input connectors (e.g. R, G, B, sync) 
from one source device, and multiple sets of output connectors, one set for 
each of a number of destination devices.  A distribution amplifier contains 
amplifiers to drive multiple 75 ohm loads without the attenuation that would 
result from "T" connectors.  Distribution amplifiers are essentially 
independent of scan rates etc., but one needs an appropriate "bandwidth".  
For Mac II 640-by-480, 60 Hz video, 10JMHz should be sufficient.  Buy one of 
these from an industrial A/V company.  

Most industrial 525-line TV equipment is provided with "loop-through" 
connectors, and one simply daisy-chains the signal through successive pieces 
of equipment without the necessity of a distribution amplifier.  But loop-
through connections are not common in computers.  If you were willing to 
modify the monitor's electronics you could accomplish the same thing, but I 
presume you don't have access to analog hardware expertise.  

I don't believe that overlay capability as suggested in <5521602MR@MSU> is 
necessary.  Also, dropping down to 30 Hz frame rate as in NTSC is not 
necessarily appropriate for pigeons .  Does anyone know their flicker 
sensitivity?  

Charles Poynton         <poynton@sun.com>
Sun Microsystems, Inc.       415-336-7846