Tuning a car radio, particularly current button-bedecked models, can be uncomfortable or even dangerous on the highway. Drivers have to take their eyes off the road and look toward the middle of the dashboard to change stations or balance the sound.
Pontiac has come up with an innovative answer to the problem. The buttons to control the radio on its sporty 6000 STE model are in the steering wheel hub. A driver can adjust the radio without having to look away from the road or moving a hand far from the wheel.
The technology that made the remote controls possible is
”multiplexing,” a system for sending different control signals down a common wire to actuate devices in the car. Engineers expect multiplexing applications to grow with each model year until the mid-1990s, when virtually all functions on automobiles will be under multiplex control.
When a driver turns on the headlights now, the switch on the dashboard makes a direct mechanical connection to complete a circuit. This means relatively heavy wires have to travel from the power source to the switch and out to the light.
On a car with a large number of power options and electronic devices, these connections produce a wiring harness resembling a fat bundle of spaghetti behind the dashboard, restricting the placement of switches, radios and instruments.
”We anticipate there will be 900 to 1,000 individual circuits on our high-line vehicles by 1990,” said Bernard F. Heinrich, a key electrical designer at Chrysler Corp. ”Each one involves wires with terminals on each end.” He estimated that multiplexing could cut the number of circuits by 35 to 40 percent.
In a fully multiplexed car, a driver wanting to turn on the headlights would press a switch that would activate a microchip that would send out a digital signal, sort of an electrical Morse code, on a wire connected to all powered components in a car.
The signal would join others traveling down this wire, called a ”data bus,” with electronic receivers at each component examining the coding preceding each ”message” to determine if it was applicable. When the signals reached the receivers attached to the light, a transistorized switch would close and the lights would go on.
”We couldn`t have done the radio controls any other way,” said Jack G. Olin of General Motors Corp.`s Packard Electric division, which developed the wheel-mounted switches. ”You can`t run 50 wires down a steering column.”
Olin said the principal advantages of multiplexing are the reduction of wire congestion in difficult areas of a car, such as the doors, and the flexibility it gives designers. Because the electronic sending units are very small, all the controls of a car, for example, could be grouped in a pod around the steering wheel.
Another advantage is in diagnostics. If a driver tried to turn on the lights and a bulb was burned out, the chip at the receiving end could put a message on the data bus to that effect. Such messages could be stored for reporting to a service technician. Or if a problem was serious enough, the driver could be alerted immediately.
