Length as specified The Problem: An engineer has contracted you to design a circuit to control gates at railroad crossings. If output Z=1 the gate lowers and lights flash to block traffic, if Z=0 the gate raises and lights turn off, allowing traffic to cross. Input A=1 if there is a special condition (such as workers present), B=1 indicates a train is coming or in the crossing, and C=1 indicates a central control command to lower the gates. The engineer asks you to build the circuit using the switching function: Z= A'B + AC 0.1 Find output for each input using a Truth Table: 200 mm (8 in) 5.2 m (17 ft) 300 mm MIN (12 in) CLEARANCE ABOVE CROWN OF ROADWAY Where gates are located in the median, additional median width may be required to provide the minimum clearance for the counterweight supports RAILROAD CROSSING Output Z Edge of background or part nearest roadway 2 TRACKS 750 mm (30 in) A'B AC C OF LIGHT 375 mm (15 in) 2.3 m (7.5 ft) MIN. 2.8 m (9.5 ft) MAX 1.3 m (4.25 ) MAX 635 mm 1(25.4 in) MAX Inputs | A B C 000 O O 1 0 1 0 0 1 1 100 1 0 1 1 1 0 1 1 1 Dimension A-B-C and length as appropriate for approaching traffic 45 1.1 m (3.5 ft) MIN. 1.4 m (4.5 ft) MAX 0.6 m (2 ft) 100 mm (4 in) MAX. ABOVE T GROUND Source: Federal Highway Administration, U.S. Dept. of Transportation https://safety.fhwa.dot.gov/hsip/xings/com roaduser/07010/sec04b.cfm For locating this reference line at other than curd section installation, see Section 10.01