* Translation by Eric Schurmann

I) From the individual towards the collective

In order to shorten calculation times, Thomas de Colmar gradually fitted clearing devices in his machines  which allowed the dials in the two series of windows to be quickly returned to zero.

The principal is ingenious: a rack, placed under the plate of the mobile carriage, turns the dials until the zeroes are showing in the windows.

The rotation does not go beyond zero thanks to an ingenious idea!  One tooth in each wheel of the dials has been removed so that, when the zero is showing in the window, the rack passes on without moving the dial!

As from 1851 the machines were equipped with a spring mechanism allowing the rack to return quickly to its initial position.

General principle

Spring	Rack + de-toothed pinions (minus one tooth)

II) Development of clearing mechanisms : 1820-1907

Model	Totalisers		Counters		Totalisers + Counters	Look
	Individual	General	Individual	General	General
T1820		X	X	X	X
T1822		X	X	X	X
T1848		X	X	X	X
T1850			X	X	X
T1852			X	X	X
T1856			X	X	X
T1858				X	X
T1860				X	X
T1865-					X
P1					X
P2					X
P3			X		X
P4			X

III) Photo gallery

Overall view of the T1850 and its clearing system

Appearance of the spring on the T1852

T1865

Clearing mechanism on the Payen type P2 totalisers

Mechanism for clearing the counters (quotients) on the Payen type P2

Combined system on the Payen type P4, around 1907