It is interesting to note that Mostek, the parent company of Corvus, had largely exited the calculator market a few months after the launch of the CheckMaster due to making large losses, but retained just that model. Distributor is JS&A National Sales Group, 4200 Dundee Rd., Northbrook, Ill. You can also use CheckMaster as an add-subtract calculator).īur.) The $40 eight-ounce unit is 7/8 by 3 5/8 x 6 3/4 inches. And CheckMaster shows the overdraft amount, if any. As you write checks or make deposits, you perform arithmetic with CHECK, DEPOSIT, and BALANCE keys. Tapped an imaginary checking-account balance into Mostek Corp.'s new CheckMaster, I was amazed to learn the electronic checkbook would remember the dollars-and-cents figures for up to one year. " Electronic Checkbook remembers your balance This model was also reviewed in Popular Science : ChackMaster operates from six 1.5-v AAA alkaline batteries." Of about 500 loads in the circuit, only about 50 are unswitched, and ion-implantation gives each of those as high a resistance and as low a power consumption as isĬonsistent with the circuit's speed requirements.Īs a result, the chip needs less than 1.5 milliamperes even when the calculator is on.
Make sure that no one device drew too much power," he says. In addition to minimising the amount of logic the memory requires, Farrier used very long depletion loads to reduce the power drain in the power-up mode. Farrier, designer of the chip.Įxtra gate to connect the output of each flip-flop in the shift register back to its input, so it looks like a cross-coupled latch as opposed to a two-phase clocked flip-flop," he says. "We went to a static shift register to eliminate much of the timing circuitry that is superfluous to storing data," comments Robert C. Key to the design of the chip is a gated-clock, static shift-register memory that draws less than 25 microamperes when Adding to and subtracting from memory is handled with "deposit" and "check" buttons Mostek has used what is essentially reverse Polish notation to eliminate "balance" key is depressed and triggers the memory-recall function. The checking-account balance is maintained continuously in the memory and is displayed when the The $39.95 unit is a two-function machine with memory. That dissipate almost as little power as complementary MOS. Mostek's CheckMaster offers proof that the company can make p-channel MOS devices "The Mostek machine, unveiled this week, is aĬheckbook calculator that will hold and display a user's checking-account balance for a year, using a single set of batteries. The journal 'Electronics', for April 3, 1975, reported the introduction of the CheckMaster :
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