Technology
Canon 161 Calculator Connected to Monitor & Control Unit
The 161 is a counter architecture machine like the 130 and is constructed in essentially the same manner but with some very important production engineering improvements.
Electronics
The electronic implementation is still based on Ge transistors and discrete diodes, nearly 800 transistors and over 2000 diodes. Circuit boards are now plugged into conventional edge connectors but the irritating base plate remains so that boards cannot be removed unless the card cage is dismounted from the base plate. Similarly, conventional extenders cannot be fitted unless the cage is released.
Display and Keyboard
These are carried over from the 130. The keyboard is composed of the same built-up leaf switches as used in the 130. The display still uses the Canon incandescent edge-lit modules, it is widened to 16 digits but the wiring harness is now terminated with edge connectors for more practical disconnection from the logic PCBs.
Monitor and Control Unit
Canon 161 Calculator Monitor & Control Unit panel
Perhaps the most interesting thing about the 161 is its connector for a Monitor & Control Unit. The counter architecture has the useful feature of being completely static, with all state preserved if the master clock is interrupted. This allows the calculator to be clocked pulse-by-pulse while individual operations are traced. The model 130 was a servicability nightmare and it seems as if the Control/Monitor unit was a response to the difficulties experienced by service engineers. A machine with such a high parts count has a statistical vulnerability to failures and anything to improve servicability would be very useful.
The unit displays 18 important internal flags and signals and allows the machine to be stepped by single clock cycles, by digit cycles or to run until a specified flag is set. The operation of the unit was reverse engineered by Brent Hilpert and the version here was constructed from his documentation. See the Data section for links to his excellent site.