One has, in any case, to bear in mind that in the recent decades, a distinction between an electronic and an electromechanical timepiece has become more and more pointless, in some case even useless. For this reason, G04C is nowadays used to classify electromechanical aspects of clocks or watches in general, without putting an excessive stress on the nature of the timepiece as a whole (for more info, see "Overlapping with external fields" below).

Although an explicit link to G04B is present in the title of G04C, documents concerning mechanical parts of electromechanical timepieces could still be classified in G04C, especially if these mechanical parts cooperate to actuate or implement electronic and/or electromechanical functions.

A typical example of such a document involves a setting crown wherein a mechanical rotation (of the crown) is transformed into a sequence of electronic pulses.

The major overlaps of G04C are found with G04G. This depends on the fact that a clear distinction between the two has become less and less possible and also less and less important. To a certain extent, G04C and G04G should be regarded as two complementary classifications, or somehow like two sides of the same coin. For these reasons, some common aspects of these two subclasses shall be discussed here.

The following 1-to-1 correspondence between G04C and G04G subclasses is to be noted:

In all of the above subclasses, documents can be found which could belong to their corresponding parallel subclass. For example, documents could be found in G04C 9/00 which could also be in G04G 5/00 and vice-versa.

When classifying, a lot is left to the common sense of the classifier. If a document describes relevant electromechanical aspects of a timepiece, this document will usually receive at least a classification symbol in G04C. The "real life" situation is such that most often documents receive a double classification (both in G04C and in G04G). Definitely, in cases of doubt, giving a classification symbol in both G04C and G04G is a preferred solution to choosing only one of them.

A typical example is given by the pair G04C 23/00- G04G 15/00. Here, timed switches, e.g., devices to execute a timed programme of switching on/off the heating system of a household are typically classified. A document showing mechanical jumpers to set the time-on and time-off, together with details concerning the mechanical connections of the jumpers with other parts of the mechanism is usually classified in G04C 23/00. Similarly, a document showing a fully programmable CPU-based thermostat with wireless connection to the main heater is typically classified in G04G 15/00.

No document concerning radio-controlled timepieces should be classified in G04C, unless other technical aspects of the documents deserve a classification therein (for further details, see the corresponding paragraph in G04G).

Documents showing internal electric and/or electromechanical means to wind a mechanical energy source such as a mainspring or a (free-falling) weight. The typical device classified here is a wall clock, pendulum clock or the like. The field has not been particularly active in the last three decades.

In particular, although the heading of G04D 7/009 is not appropriate, the winders for automatic watches are classified in that group and not the G04B 5/00.

There could be overlap between G04C 3/001 and subgroups and G04C 9/00. Hence consider this when searching G04C 3/001 and subgroups. For more details concerning this overlap, see the section concerning G04C 9/00.

When searching in G04C 3/06 and subgroups or G04C 3/08 and subgroups consider whether it is the case to extend the search in G04C 5/00 (electromagnetic escapements).

For practical reasons, G04C 3/14 and subgroups comprises also documents concerning step-motors per se, if these motors are used nowhere else than in timepieces. Therefore, a natural overlap with H02K 37/00 (general group for step motors) does exist. When searching in G04C 3/14 and subgroups, this overlap has to be considered, on a case-by-case level.

The same applies to G04C 3/12 and subgroups, the general group for piezoelectric actuators being H10N 30/00 and piezoelectric actuators being also found in H02K 33/16.

Documents dealing with setting the time (and/or the date) in an electromechanical timepiece or, by electromechanical means, in an electronic timepiece. With the exception of G04C 9/02, the key element of G04C 9/00 is a setting crown.

G04C 9/02 contains still many radio controlled timepieces (which are nevertheless all double classified and shall be soon removed from here) and, in addition, it contains documents showing systems allowing to test/correct the running precision of a timepiece by establishing a wireless communication between the timepiece and an external control device. Typically these control devices are available in the timepiece manufacturing site or by retailer shops, to perform calibration or re-calibration of some (otherwise inaccessible) of the timepiece elements.

Documents classified in the rest of G04C 9/00 should, as a general rule, contain details concerning the operations that a user needs to perform in order to set the time. On the contrary, if a document merely contains hardware details concerning the electromechanical setting element (the crown, most typically), then classification in G04C 3/001 and subgroups should be considered. In the past, this has not always been the strict policy, therefore an overlap still exists and should be always considered.

Documents showing details of the power supply of timepieces. These details generally concern:

Due to the non-existence of a corresponding group in G04G, many documents concerning details of power supplies of purely electronic timepieces can still be found in G04C 10/00 and/or in G04G 17/04. This should be borne in mind when searching these groups.

Similarly, if a document contains details of power supply circuits, it may be classified only in G04G 19/00, even if it concerns an electromechanical timepiece or an electronic timepiece with mechanically moving parts.

Master-slave clock systems wherein, as a general rule, the slave clocks are not autonomous clocks and they constantly need driving signals issued by the master clock in order to deliver time information.

Details of the master clock part.

Details concerning slave clocks.

Documents showing electromechanical time displays. The groups/subgroups are defined in terms of the technical features used to display time (bands, flaps, drums, etc).

When searching in G04C 17/0091, extension of the search to G04G 9/0082 is necessary.

G04C 17/00 is the subclass of G04C having the highest overlap with G04B. Therefore, extension of the search in corresponding parts of G04B should always be considered, especially if the search concerns the manufacturing methods of the mechanically moving parts.

The title of this subclass contains the expression "at predetermined times".

This is an important aspect because this subclass contains documents describing timepieces producing a visual action at a predetermined time of the day.

This means that countdown timers which would count-down a predetermined time interval independently on the time of the day are not part of G04C 19/00, but rather G04F 1/00, G04F 3/00.

See G04C 23/00

Likewise G04C 19/00, only with acoustic output instead of visual.

This subclass also contains the group G04C 21/04 which features the electromechanical version of the so called "minute repeater" complication.

See G04C 23/00.

Documents related to timepieces providing an electromechanical action (non visual, nor acoustic) at predetermined times (of the day). It also extends to the possibility to act after the elapse of a predetermined time interval which is nevertheless counted starting from a predetermined time of the day.

This subclass completes a triplet with G04C 19/00 and G04C 21/00.