1.5.2 Timer. 1  Before the kernel begins executing user code, a timer is set to generate an interrupt. 2  The timer interrupt handler reverts control back to the kernel. 3  This assures that no user process can take over the system.  Timer control is a privileged instruction, ( requiring kernel mode.
The Liberty Bell was cast in the Whitechapel Foundry in London and hung in the belfry of the Pennsylvania State House in 1753. That building is known today as Independence Hall. The bell cracked upon its first use before being recast twice by John Pass and John Stow, of Philadelphia. You can see their names inscribed on the bell as well as a Biblical verse from Leviticus, Proclaim Liberty throughout all the Land unto all the Inhabitants thereof..
Liberty Tree Site. One block east of Boylston Station (Green Line) and Boston Common, at Washington and Essex Streets, is the site of the famous Liberty Tree. Embedded in the wall of the building located at 630 Washington Street is a tablet marking the spot of the historic landmark, bearing the inscription Sons of Liberty, 1766.. At the time of the revolution, a great elm tree stood in front of a grocery store here.