Running Modes
There are five different running modes for generating timecode.
The most basic setting is Free Run / Time of Day. That means that the internal timecode generator is like a clock, denoting the actual time of day. The clock runs continuously, whether the tape is recording or not. This is convenient setting to use, since anyone who needs to note the timecode numbers only has to gaze at his or her own wristwatch. Timecode errors between the slate and the recorders are obvious and easy to detect.
(It is interesting to note that some studios and producers object to time of day timecode because it is a permanent record substantiating overtime claims by the crew.)
The next most common setting is Free Run / User Set. This is similar to the above setting, except that the starting time for the TC generator is chosen by the user and does not correlate to actual time of day.
Commonly, the Hours digits are used to signify sound roll number. Spare wristwatches can be reset to match the timecode generator, if you have people on the set who need to keep track of the code.
Record Run timecode means that the generator stops when the tape does. Numbers increment during the Record mode, but remain frozen in time during pause or stop. The elapsed timecode is sort of like a tape counter, and is an indication of how many minutes have been recorded. Users often use the Hours digits to indicate reel number, rather than an "hour" of the day.
The difficulty in using Record Run is that all of the timecode generators (i.e. camcorder, audio recorder, timecode slate) would need to be physically connected to each other at the start of every take. This would necessitate a lot of cabling, or a complex set of wireless transmitters & receivers. Not for the impatient nor the feint of heart.
The last two "modes" are External and Jam-Sync.
External refers to continuously reading timecode from an External source and re-generating it onto the tape. If the External code should stop or be intermittant, the code being recorded would also be in error. (Many recorders are programmed with a self-protection that would automatically jam-sync to the last good code and begin generating new code in the absense of the External code.)
Jam-Sync (a.k.a. Set from External) means that the recorder synchronizes its internal timecode generator to match the starting numbers from an External source. When the connection to External is released, the internal code will keep in step with the external timecode source for a few hours or longer, depending on the accuracy of the timecode generators in question (recorder and source). Of course, Jam-Sync only makes sense in the Free-Run timecode modes.
