Let us now consider some of the problems in the Subpart H requirements which apply to TV Games. There are five types of tests covered by Subpart H:
(1) Measurement of the spectral amplitudes of magnetic or electric (depending on frequency) fields being radiated from the game (including ac adaptor, if so equipped, ANTENNA/GAME switch, and interconnecting cables).
(2) Measurement of the spectral voltages which appear on the ac or dc power line.
(3) Measurement of the spectral voltages which are applied to the terminals of the TV set.
(4) Measurement of the isolation of the "transfer" (i.e., the ANTENNA/GAME switch, at the channel frequencies for which the game is designed to be used.
(5) Measurement of the amplitude of the modulated carrier which is applied to the terminals of the TV set, at the channel frequencies.
Consider first the test which measures the levels of radiated electromagnetic emissions, number (1) above. The high degree of subjectivity in the method used to perform this test makes it very difficult for the engineer to know whether he has over or under-designed. During the test, the FCC moves the various cables over and around the game in a variety of arbitrary configurations, looking for a "worst case" configuration. It is not unlikely that no matter how hard the manufacturer (or independent test lab) has looked for this worst case condition, the FCC, if they spend enough time at it, will be able to find a particular orientation of game and cables which results in a higher level of radiation than the lab found. In the context of EMI qualification testing procedures, this is the only radiation test in the world which allows the arbitrary placement of the various elements of the item being tested. But the only way in which this situation will be changed is for the Games Industry to research the alternatives, and to present these alternatives to the FCC in a "Petition For Rulemaking” procedure, complete with a strong technical rationale.
The second test in our list has a hidden pitfall for the Games Industry. In an effort to lower the per-unit cost, some manufacturers have offered various models in their line of battery-operated games for sale without an ac adaptor. Apparently they reason (probably correctly) that the game will most likely be operated on batteries by most purchasers, and that the few who do want to operate from household ac power can then purchase an optional ac adaptor. This being the case, there is no reason to make the majority of buyers pay for ac adaptors they will never use. However, in the Type Approval process, two games which are in all respects identical except for the inclusion with one of an ac adaptor, must according to the FCC, each undergo its own Type Approval. Now comes the clinker: Because of the nature of the test setup, the game which uses the ac adaptor will exhibit much lower levels on its ac power connection than the battery powered game will show on its dc power input (which
–150–
