Note : PTT stands for Postes, Telegraphe, Telephone . Former initials of the French postal administration.

A long time ago ...

The administration of PTT services usied switchboad operators to link two subscribers . they use to fill a form that identified the subscriber responsible for the appeal and, depending on the distance and the corresponding duration of telecommunications, information elements for the accounting department to establish billing.
In the late 40s, the number of subscribers increases, the PTT administration generalized the installation of automatic switchboards using electromechanical counters (one counter being assigned per subscriber ) to record telephone units consumed and establish billing . Manual reading of meters becoming tedious, an order was made to OPL Foca for supplying photographic apparatus adapted for the pickup images of the counters mentioned above .

To meet the required specifications O.P.L. proposed to the PTT administration , based on a model PF1 bis  , the following modifications :

• The format modified from 24 x 36 to 24 x 30 (mm) .
• The frame counter is modified to identify up to 42 views .
• The shutter offers only one speed : 1 /25 second.
• Ergonomic changes in the cocking shutter button and the rewind button ( may be different depending on the model ) .
• The presence of four centering pins to ensure correct positioning of the camera on the carrier which was presented in front of the chassis containing counters .
• A 50 mm lens  ( 3.5 to start, OPLAR 2.8 and later and finally some OPLEX 2.8) with fixed draw and with the aperture control ring clamped to an opening (between f 6.3 and f 9) .
• On some models, the presence of an intermediate ring to increase the draw.
• On some models, the presence of a metal cap prohibiting the use of the flash sync .
• the presence in front of a ( A / R ) system for rewinding. It was maintained even when OPL provided cameras based on the model "Standard" for which this function was replaced by another command as a standard .
• On some models, the presence of a specific marking, specific to the PTT administration.

In 1953, in the Parisian switchboard  (of the ROTARY type ) the first Foca PTT were used .

The adjustments listed above allowed an employee with no knowledge in photographic practice to operate and allowed also to avoid handling errors by ensuring some homogeneity in the records. All these characteristics allowed to photograph 25 counters at a time . Some cameras were equipped with the flash synchronization adapted to the use of a light box of the type Philora (mercury vapor lamp) and later to the use of an electronic flash . The operator began each session taken by a photograph of a device identifying the switchboard identification and a timestamp . Once the film were developed, they were provided to the accounting services using an amplifier of the style of those used for reading microfilms and , based on the previous statement , established bills to subscribers. An article in "FOCAGRAPHIE" indicates the use of more than 100,000 views per year per camera.

Experts are still conjecturing on the number of such modified Foca. Today these models are still relatively uncommon even if much more had to be thrown by employees using this equipment when it was discarded. Indeed these modified devices could not used to anything else than the photography of switchboards counters. Moreover, after long and loyal service they were relatively " tired " and no longer had the freshness of their youth.

When O.P.L. withdrew from the market of manufacturing cameras in the middle of the 60s , the PTT administration used equipment from other manufacturers whose Leica ( a priori commercial devices on a trial basis ) , Pentax ( K1000 ) . .. The generalization of electronic switches made ​​useless the photographic records.

This type of installation and the means to record counters values is not the prerogative of the PTT administration . Other phone networks in Germany ( the BUNDESPOST ) , the Netherlands , Sweden , Monaco, ... used similar facilities and appealed to other manufacturers of cameras for the same functions. Mention may be made of Leica (Ic , Ig , MD Post, Post MDa , M4 Post ) , Alpa (11a) , Pentax ( K1000 ) ...