The movements are characterised by:
- Balance Wheel with an iron segment
- A fixed coil
- Mechanical contacts
As the balance turns, just as the iron section is approaching the coil, it closes the circuit and the core of the coil is magnetised causing the balance to receive an impulse. As the iron section on the balance passes the coil, the circuit is broken. The balance spring ensures there is a reverse impulse and the cycle then repeats itself.
Unlike the Moving Coil System, Contact Controlled movements, these often have a diode to reduce sparking on the contacts and therefore prolonging their life. The presence of this diode allows these watches to be rightly called the first “electronic” watches.
In my experience, these movement are much more robust than the moving coil system type. On the latter type, it is very easy to damage the coil on the balance through careless handling.
The first set of photographs cover the LIP R 148 movement. It first appeared in September 1961 and was a great improvement over its predecessor, the LIP R 27. The LIP R 148 can be seen in the following watches: Belforte, Benrus, Stowa, Vulcain and Waltham
This second set of photographs cover the Landeron 4750. It is actually an Ebauches SA (ESA) movement but was named after the ESA branch that developed it. Unlike the LIP above, this movement has 4 iron segements on the balance and the coil is semi-circular and embedded in plastic, but the working principles are the same. In the detailed photograph (balance removed), you can see the pair of contacts.