rob's changes 010

basic_concepts/index.html

@@ -255,6 +255,8 @@ A good starting point for newcomers in the electronics field looking for what is
 
   - ####Capacitors in filters:  low pass and high pass.
 The charging and discharging of the RC combination makes capacitors useful as frequency filters.
+Discussion of symbol for ground used in the circuits below.
+
 
   ![CPC](imgs-filippos/lp_hp.jpg)