diff --git a/tech/GSM.wiki b/tech/GSM.wiki
index 062ea6b..92c93c6 100644
--- a/tech/GSM.wiki
+++ b/tech/GSM.wiki
@@ -3,6 +3,24 @@
 GSM or the global system for mobile communications is a standard developed to
 standardize cellphones and their communication and infrastructure.
 
+GSM handsets derive the baudrate from very very accurate clocks on the base
+station.
+
+== Bands ==
+
+GSM occupies 
+
+* 850 (USA)
+* 900 (europe)
+* 1800 (europe)
+* 1900 (USA)
+
+*NOTE* GSM-900 uses 880-914mhz
+The 33cm ham band is 902-928mhz. Therefore, for 902-914 we can transmit legally
+as a eurpean tower.
+This band is also the ISM (industrial scientific medical) band. Most devices on
+this band are low power and low utilisation.
+
 == IMSI ==
 
 International Mobile Subscriber Identity is a way for devices to id themselves
@@ -12,3 +30,6 @@ on a GSM network. An IMSI is a secret key that is stored on the SIM card.
 
 A spoofed GSM tower. In GSM the base station (tower) picks all settings
 including Tx power, Rx gain, encryption, etc
+
+When the tower tells the handset to disable encryption (A5/0), and handset
+_should_ tell user about this. Hoever every manufacturer disables this