On 24/03/2016 16:28, Lawrence Stewart wrote:
> And the keyboard locks!  You cannot press a key unless the machine has finished transmitting the
> previous key.  “two key rollover” was a great advance in its day.

In the late 1970s or early 1980s I worked over a summer in a repair shop 
for equipment manufactured by the German company Kienzle Apparate GmbH. 
Their keyboards were a marvel of electromechanical engineering. When a 
key was pressed the remaining keys were *physically locked*, preventing 
a second key from getting pressed. This was supposed to provide the 
operators with tactile feedback when they accidentally pressed more than 
one key. Maybe gratuitous over-engineering, such as this, contributed to 
the company's decline and the eventual takeover by Manessmann (1981) and 
then DEC (1991).