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..
We hired a driver to take us to touristy spots, and the Liberty Bell and the Independence Hall was one stop. He pointed to a building over there for the Liberty Bell, but we were still clueless. I thought it was an open area with a bell, sort of like the Plymouth Rock.. out in the open.