+# About the ANI/DNIS/*Number columns:
+# For inbound calls, ANI appears to be the true source number.
+# Usually ANI = TermNumber in that case. (Case 1a.)
+# In a few inbound CDRs, ANI = OrigNumber, the BillToNumber is also
+# the DialedNumber and DNIS (and always an 800 number), and the TermNumber
+# is a different number. (Case 2; rare.)
+#
+# For outbound calls, DNIS is always empty. The TermNumber appears to
+# be the true destination. The DialedNumber may be empty (Case 1b), or
+# equal the TermNumber (Case 3), or be a different number (Case 4; this
+# probably shows routing to a different destination).
+#
+# How we are handling them:
+# Case 1a (inbound): src = ANI, dst = BillToNumber
+# Case 1b (outbound): src = BillToNumber, dst = ANI
+# Case 2: src = ANI, dst = DialedNumber, dst_term = TermNumber
+# Case 3: src = BillToNumber, dst = DialedNumber
+# Case 4: src = BillToNumber, dst = DialedNumber, dst_term = TermNumber
+