By Richard G. Merrell, Zenith Electronics Corporation
The undesirability of requiring a viewer to juggle several transmitters in attempting to control his decoder, VCR, and TV receiver has long been recognized. Early attempts to alleviate this problem developed transmitters which could control two units provided the units were from the same manufacturer and the user could remember to operate a slide switch or shift key to select which device was to be controlled. More recently, various manufacturers have developed units which can control VCR's, television receivers, and decoders from more than one manufacturer. One technique used for this is to "train" the transmitter to generate the proper IR format by exposing it to the IR codes that it is to replicate. A second approach is to program algorithms for generating different IR formats in firmware and then provide some means of tel ling the device which algorithm to branch to when it is to transmit, say, "Channel Up" for a decoder or "Pause" for VCR. The shift key or side switch inconvenience could be eliminated by providing separate keys for all functions, but this would make for a very crowded keyboard. An improvement on this is to retain the slide switch but provide multiple keys for such functions as "On/Off", thus minimizing the need for operating the switch.