A Prontor-Compur connection (also known as a PC connector, PC terminal, or PC socket) is a standard 3.5 mm (1/8") electrical connector (as defined in ISO 519) used in photography to synchronize the shutter to the flash. 

""Prontor"" has its origins in the Italian word "pronto", meaning "ready" (and was a leaf shutter made by ). ""Compur"" is derived from the word "compound" (the """" was a long-lived series of leaf shutters made by ). 

The term is derived from brands of widely marketed photographic leaf shutters manufactured from the early 1950s by two distinct, but now defunct German companies. (which made the "Prontor-S" and "Prontor SV" models, amongst others) and (the "Synchro-Compur" model, successor to the "Compound" model). 

Both companies' brands, "Prontor" (from 1953) and "Compur" (from 1951), shared a common 1/8"-inch coaxial connector for shutter/flash synchronization. This convergence of design is not as coincidental as it might first appear, owing to the fact that the Zeiss organisation held a significant shareholding in both of these companies prior to the introduction of the shared connector. By the 1950s, Gauthier were manufacturing up to 10,000 "Prontor" shutters daily. 

The Gauthier company's essence lives on as , which is a wholly owned subsidiary of . The Deckel company went bankrupt in 1994.
What is also known as a protector?
What kind of protector?
What is the usual size?
Is this unusual?
Where does the term Prontor come from?
What is the connector used for?
Of what?
What is the word Compur from?
What is it the name of?
When did Prontor originate?
And Compur?
Are they totally different from one another?
What is alike about them?
What did this aid the item in achieving?
Who had a major interest in the brand?
Who was the manufacturer?
Did they make 20,000 a day?
How many did they make per day?
Is the company still creating these today?
A Prontor-Compur connection
A Prontor-Compur connection (also known as a PC connector
A PC connector
A Prontor-Compur connection (also known as a PC connector
3.5 mm
is a standard 3.5 mm (1/8") electrical connector (as defined in ISO 519)
no
is a standard 3.5 mm (1/8") 
Italy
Prontor"" has its origins in the Italian word "pronto"
Synchronization
used in photography to synchronize the shutter to the flash. 
A shutter to the flash in photography
used in photography to synchronize the shutter to the flash. 
The word compound.
"Compur"" is derived from the word "compound" (
A series of leaf shutters.
" (the """" was a long-lived series of leaf shutters made by ). 
1953
Both companies' brands, "Prontor" (from 1953) 
1951
Both companies' brands, "Prontor" (from 1953) and "Compur" (from 1951),
No
shared a common 1/8"-inch coaxial connector for shutter/flash synchronization.
shared a common 1/8"-inch coaxial connector
shared a common 1/8"-inch coaxial connector for shutter/flash synchronization. 
for shutter/flash synchronization.
 shared a common 1/8"-inch coaxial connector for shutter/flash synchronization.
Zeiss organization
 owing to the fact that the Zeiss organisation held a significant shareholding in both of these companies prior to the introduction of the shared connector
Gauthier
Gauthier were manufacturing up to 10,000 "Prontor" shutters daily. 
No
 Gauthier were manufacturing up to 10,000 "Prontor" shutters daily. 
up to 10,000
 Gauthier were manufacturing up to 10,000 "Prontor" shutters daily. 
No
The Gauthier company's essence lives on as , which is a wholly owned subsidiary of . The Deckel company went bankrupt in 1994.