Flash Synchronisation


Cameras usually have a mechanism to synchronise the firing of the flash with the shutter release. In mechanical cameras such as the Olympus Trip 35, this synchronisation occurs through a micro switch. When the shutter releases, the mechanism also trips the switch briefly closing its contacts. A flash unit uses the closing of these electrical contacts as a cue to fire.
This switch system, known as "X syncro", was very popular with the Olympus cameras, and the principle is the same for most makes of mechanical cameras. Other cameras use the term "X-sync", and "X-contact", which implies a switch associated with the shutter mechanism. These types of switches are for electronic flash systems and they are synchronised to operate exactly when the shutter is open.
On the Olympus Trip 35, the switch contacts are available through two different types of sockets with the same wire soldered to both.
Circuit Diagram of Switch Contacts

As you can see from the circuit diagram, the switch, and sockets have a common chassis earth, because the chassis is made of metal. The other switch terminal connects to the centre pins of the sockets.
Prontor / Compur (PC) Socket

The Prontor / Compur socket is a widely accepted standard for the transmission of electrical signals to facilitate interfacing a flash unit. The electrical signal is a switch connection, which provides a cue to the flash unit.
The switch contacts are available through a 3.5 mm PC socket, and usually, the flash unit that connects to it tends to use a coaxial wire for this connection.
Accessory Mount – Hot Shoe Socket

The accessory mount, also known as a "hot shoe" socket, is compatible with cordless flash units. The socket has a metal terminal at the centre, which connects to the switch.