versatile digital clock

Elektor has previously published designs for `one-chip` digital clocks, with both mains and crystal reference frequencies. Whilst ICs such as the MM5314 are excellent for simple timekeeping, they have certain disadvantages. Since the output to the display is multiplexed the time output of the clock is not easily accessible in a parallel form. This means that the clock is unsuitable for driving time-controlled devices such as alarms, calendars, central heating programming, automatic recording of radio programmes or other systems. The clock described in this article is based on TTL circuitry and is eminently suitable for control systems. The time is available as a BCD coded output, and clock pulse trains with rates varying from one a second to one a day are obtainable. Many constructors will probably have some of the ICs in their `junk box`.