Abstract: A bank of counters is clocked at a relatively high repetition frequency by a clock oscillator. Each counter separately produces a sequence of digital signals which are transmitted at the clock oscillator frequency by a latch and a decoder/driver associated with the counter to a numeric display also associated with the counter. Consequently, the digital signals produced by each counter are separately displayed at the clock oscillator frequency. This frequency is sufficiently high to prevent recognition of a number on the display. A bank of manually operable momentary switches is associated with each latch. A brief audible tone is produced whenever a switch is operated. When operated, the switch temporarily disables the associated latch for a preselected interval of time. When disabled, the latch transmits only the digital signal currently stored in the latch to the display for the preselected interval of time.