Polarity and Pinout
1N4937 diode has a cathode (-) and anode (+). In the schematic symbol, the tip of the triangle with the line on top of it is the cathode. The cathode is marked on the body of a diode by a band as shown below.
Diode polarity Current can flow from the anode to the cathode only and never from the cathode to the anode – 1N4007 diode is like a one way valve.