Are there sensors on the rear brakes?

When changing the rear pads the other day on the '85 300TD (wagon) I noticed no sensor wires to be replaced. And the pads had no hole for a sensor wire like the front brake pads have.

If no sensors on the rear brake pads I'm curious as to why just the front...?

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JWJ
1983 MB 300D - > 430,000 miles - Deep Blue - Bilstein Comforts - 0-60 in 24 seconds - 27MPG
1985 MB 300TD (wagon) - > 275,000 miles - Manila Beige - Thule rack - 0-60 in 18 seconds - 22 - 25MPG
Biodiesel, Mobil Delvac 1, and Viton fuel lines!