First came ATS (automatic train stop), in 1880, using an arm connected to a semaphore blade to to smash a glass tube on the locomotive which was connected to the brake pipe (the Vogt system). This later morphed into track side tripper arms which tripped open a valve mounted on the truck near the leading wheels. Electro-magnetic versions came out in 1914 using auxiliary contact rails.The inductive versions came out around 1922, of which the AT&SF system is the most well known. Cab signals date to 1914, using those contact ails, and the inductive system dates from 1926. The speed control came later (the speed control apparatus is on the locomotive, not the wayside stuff)..

Briefly put:
ATS = Automatic Train Stop (trippers or inductive)
CSS = Cab Signal System, inductive, which doesn't necessarily include speed control
ATC = Automatic Train Control, cab signals with speed control
PTC = Positive Train Control, which is that magical panacea that's going to save us all. Some versions use GPS, others like ASES and ASES-II don't. The ACSES system was first developed in Europe.