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You need some digital comparator ICs, such as the 74LS85 or 74LS688, and four rotary BCD switches, one for each digit.
The inputs to the comparators connect to the outputs of the counters and the BCD switches. The comparator's output will go high when both inputs are equal to each other, this sets off the alarm - connect a piezo buzzer to the output of the binary comparator.
The comparators need to be cascaded so they behave like one comparator, this is easier for the 74LS85 (it's shown on the datasheet) but you need to use four ICs, as they're only 4-bit comparators and you need a 16-bit. For the 8-bit 74LS688 but it should be fairly easy to add a gate to the P=Q outputs so the buzzer is activated when both ar low. I probably wouldn't bother with using another IC and would use a combination of diodes and a transistor, ask if you don't know how.
What's the mains frequency in your area? If it's 50Hz, you'll need to modify the circuit: change the divide by 6 counter to divide by 5.
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