Timer Services - an interrupt handler set up by the RTOS which counts ticks on each interval timer interrupt and signals any threads that have reached a timeout threshold.
Time-slice - a unit of CPU called a quantum which can be allocated to a thread in a preemptable best effort system - in these systems timer services often makes a call into the scheduler on each system tick in order to provide quantum preemption - so, the tick, a quantum, and timeout resolution are typically all the same - e.g. Linux/Unix scheduling.
Top Half - the interface presented to calling threads/tasks/processes by a driver. The Top Half includes thread control features such as blocking (using a semTake most often) and policy such as how many threads it will allow to read/write a device at once.
Trace - a linear buffer with records that include time (cycle count) and state information for a processor core and/or application code.
TTL - Transistor to Transistor Logic - traditional 5v digital logic levels. Also, Time-To-Live - A counter in a datagram that is decremented on each node-to-node hop such that the packet is discarded when TTL=0; this prevents a packet from hopping around the network indefinitely and creating a problem.