diff --git a/tech/GSM.wiki b/tech/GSM.wiki
new file mode 100644
index 0000000..062ea6b
--- /dev/null
+++ b/tech/GSM.wiki
@@ -0,0 +1,14 @@
+= GSM =
+
+GSM or the global system for mobile communications is a standard developed to
+standardize cellphones and their communication and infrastructure.
+
+== IMSI ==
+
+International Mobile Subscriber Identity is a way for devices to id themselves
+on a GSM network. An IMSI is a secret key that is stored on the SIM card.
+
+=== IMSI catcher ===
+
+A spoofed GSM tower. In GSM the base station (tower) picks all settings
+including Tx power, Rx gain, encryption, etc
diff --git a/tech/Ham.wiki b/tech/Ham.wiki
index 00822d2..e2e4918 100644
--- a/tech/Ham.wiki
+++ b/tech/Ham.wiki
@@ -52,3 +52,8 @@ See [[Radio_Etiquette]]
 [[Gnuradio]]
 [[Hack-RF]]
 
+
+== Also see ==
+
+* [[GSM]]
+