ing instantaneous pre-selection of station frequencies, the card serves as a permanent memory since the code generator's volatile memory loses the station code when power is turned off.
Trend to Complexity. The trend in consumer electronics is toward greater circuit complexity made possible at low cost due to the use of integrated circuit technology. The circuit designer gains flexibility in achieving performance goals and operating convenience for the customer. Unless proper steps are taken, however, servicing of this type of equipment can become a problem as troubleshooting time and test equipment expenditures increase drastically.
The best approach seems to center around modular construction with each module representing a functional sub-assembly which can be replaced with no more effort than the vacuum tube in an old TV set. Fault location is greatly simplified by the fact that each module performs a definite function which can be monitored individually with a minimum of test instruments. Once the faulty module is replaced by the service shop, it is sent back to the factory where automated test facilities localize the fault to a component on the subassembly and it is either repaired or scrapped. This module exchange policy has been used for some time and is gaining in importance as equipment complexity increases. The customer also has the advantage of knowing exactly how much the repair will cost if it is done after the warranty period has expired because definite module exchange prices have been established. Even service shops with limited facilities can repair a unit as complex as the digital FM tuner if a set of PC modules or even another operating unit is available. Each module is simply interchanged with a new one until the fault disappears.
Although the complexity of circuitry has increased, reliability has increased also. Through the use of MSI (medium scale integration), the number of hard-wired interconnections has actually decreased thus avoiding a significant number of failures. By screening TC's in incoming inspection, testing assembled modules under worst case conditions before they are mounted into complete units, and extensive life testing of finished products, the failure rate has been reduced to a fraction of what it was a few years ago. The IC's used as building blocks in the digital sections are of the standard variety already well proven in the computer industry and second sourced widely.