Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!apple!oliveb!sun!vector!poynton From: poynton@vector.Sun.COM (Charles Poynton) Newsgroups: comp.sys.mac Subject: Re: Help w/Mac II Video Output Summary: To "split" video you need a "distribution amplifier". Message-ID: <93607@sun.uucp> Date: 13 Mar 89 05:31:19 GMT References: <5521602MR@MSU> <5521602MR@MSU> Sender: news@sun.uucp Lines: 29 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 Sun Microsystems, Inc. 415-336-7846