US 4569017 A This circuit provides for synchronizing the
internal clocks of at least two central processing unit process
controllers. In order to synchronize the internal clocks of
these central processing units (CPUs), the CPUs periodically
execute a predetermined set of operating instructions which
cause their internal clocks to coincide. This synchronization
function is dynamic in that it is continually performed in an
on-line fashion while the processors are performing their
telecommunication process control function. 1. In a
telecommunication system, a CPU synchronization circuit is
connected to a clock of said telecommunication system, said
clock being operated to produce at least first and second
periodic signals, said CPU synchronization circuit comprising:
CPU means including at least first and second non-synchronized
CPU copies; each of said CPU copies including: a first clock
input lead connecting said clock to said CPU copy and being
operated to transmit said first periodic signal to said CPU copy