There are numerous ways to do that. Here are a few simple and useful examples. 1.And 2.The diode protects against wrong polarity-voltage. C filters the DC-current from your regulated power or batteries. 3. When building several units into a rack, one malfunction unit can blow the fuse, so all the rest will die! You don't want that to happen! If one unit fails and a shortcut occurs then hopefully the resistor burns off,saves the other units from shutoff. Maybe it's enough with a 1n4148-Diode (max current=150mA) In practice however, the regulators may shut down because of the high current flow(regulators internal protection). You only have to restart the power-supply after a few seconds. Then everything will work except for the malfunction unit. When you use relay as bypass switches they will automaticly go to bypass-mode when voltage drops.(If you wire them correctly!) 4. Easy way to protect against wrong polarity. 5. Protect your Germanium transistors in this way..or other valuable circuits! 6. Use 1 and 2 always when you build something. C may be increased in value depending on hum,noice that may be occuring in your circuits. 7. Add a 100Nf condensator close to each supply-terminal on each op-amp. Helps supressing high frequency-peaks and violent neighbours! How to protect your constructions.
That's it for now! Let me now if I have made any errors!
Stellan