Delay-interval selection for a digital delay generator

Claim 1

In an oscilloscope, a digital delay device including a digital delay register for storing a value representing a preselected delay interval, clock means for generating counting pulses at a preselected frequency, counting means for counting the pulses from said clock means up to a number of pulses determined by the value stored in the digital delay register, and for generating an output pulse when said number of pulses has been counted, and a start delay control for sending a start count signal to said counting means; the improvement comprising: a plurality of up/down decade counters, each having a count direction input, a clock pulse input, a plurality of digit outputs, and a tens carry output, the tens carry output of each counter being connected with the clock pulse input of an adjacEnt counter; a voltage source for supplying increment and decrement voltages to said up/down decade counters; an increment/decrement clock pulse source for supplying pulses to be counted by said up/down decade counters; a plurality of switches, each connected to a corresponding up/down decade counter, each switch having three positions, an increment position for connecting the increment/decrement clock pulse source to the clock input of a corresponding decade counter and an increment voltage from the voltage source to the count direction input of a plurality of decade counters, a decrement position for connecting the clock pulse source to the clock input of said corresponding decade counter and a decrement voltage from the voltage source to the count direction input of a plurality of decade counters, and a third position for making no connections.