sumlock anita 811

here is the anita 811 from 1974 by sumlock comptometer ltd, uxbridge.

similar to the 810 but with a memory. a switch is required to activate the memory which then accumulates a total whenever equal is pressed. rm recalls the memory value and if switched off, the memory retains its value throughout further calculation. this appears to be the only point of the switch.

the design is rather nice, cool 70's retro with a red led display and brushed aluminium back that slides off to reveal a battery compartment that holds three AA cells. a socket in the top of the unit accepts the optional mains adapter.

the unit operates in a manner unconventional today. calculation is performed like a desk calculator so that 2+3+ adds 2 and 3 (rather than 2+3=). equals is for multiply, so that 2*3=+4+ performs 2*3+4=. this seems a bit odd at first, but it can lead to some useful optimisations. the later, scientific 841 did not operate this way.

here is also the anita rounding feature activated by the switch with the rounded logo. in this mode, all calculations round to two decimal places.

click on the calculator to run simon southwell's anita simulator. more info here.
the manual and laminated quick reference card are the same size as the machine and fit neatly with the unit inside the handy leatherette tab fold case.