What are synchronizers?

Some articles on synchronizer, synchronizers:

Audio Synchronizer
... An audio synchronizer is a variable audio delay used to correct or maintain audio video sync or timing also known as lip sync error ... The audio synchronizer receives the DDO signal and in response delays the audio by an equivalent amount, thereby maintaining proper audio video sync ... Modern audio synchronizers operate by digitizing and writing the audio signal into a ring memory, which is most commonly a RAM-based memory having independent read and write ability ...
GM F40
... Triple-cone synchronizers are used on 1st and 2nd gears ... These synchronizers have three friction surfaces, which increase their ability to transfer the flow of torque more smoothly from one gear to another ... Synchronizers act as clutches to speed up or slow down the gearsets that are being shifted to, and greater friction area results in easier shifting for the driver ...
Synchronization - Uses
... There are also electronic digital circuits called synchronizers that attempt to perform arbitration in one clock cycle ... Synchronizers, unlike arbiters, are prone to failure ... Automotive transmissions contain synchronizers which allow the toothed rotating parts (gears and splined shaft) to be brought to the same rotational velocity before engaging the teeth ...
Anatomy of A Truck - Drivetrain
... either an automatic transmission or a manual transmission with synchromesh (synchronizers) ... Bigger trucks often use manual transmissions without synchronizers, saving bulk and weight, although synchromesh transmissions are used in larger trucks as well ... Transmissions without synchronizers, known as "crash boxes", require double-clutching for each shift, (which can lead to repetitive motion injuries), or a ...