Electronic parking time indicator - has clock oscillator and three stage decade counter with display

摘要

The electronic parking disc indicates parking time in minutes, regardless of the time of the day and may comprise integrated circuits or discrete circuit elements. An I.C.- clock oscillator is connected so as to generate one minute pulses. These pulses clock a three stage decade counter counting ones, tens and hundreds input pulses up to a maximum of 199 minutes. The counters are connected to an l.e.d. or, for economy, and l.c.d. display. An additional combinational logic stops the oscillator (2240/10-1) and resets the counter (4026/15-1). Switching off the ignition starts the oscillator (2240/10-0) and enables the counter (4026/15-0).