V-Tap ISDN PRI Manual EN v1.3 Okt 2018 © 2018 Vidicode 26
SD File Encryption
By default, the WAV files on the SD card can be played by any media
player. By enabling the file encryption, the files only produce noise.
The file encryption uses the same Encryption Password as the Tunnel
encryption.
SD Max Files on Card
The maximum number of files on the card has 2 purposes.
First, it makes the directory on the card more manageable by the
system and any PC. Too many files in one directory make a slow
system. The default number of 10000 is reasonable.
Secondly, a system can be built to use the card as an endless buffer,
without the problem that the card is getting full. However, this must
be calculated carefully and depends on the size of the card and the
maximum file size (see below. After the maximum number of files
has been reached, the file write-counter is reset and older files are
overwritten automatically.
The maximum tested size of the SD card is 32 GB and it must be
formatted with the FAT32 file system.
SD Max File Size in MB
When a file on SD card reaches the maximum file size, the file is
closed for further writing and then send to the Tunnel server, if that
function is enabled. The name counter is incremented at the same
time and a new file is opened.
An ISDN recording produces 8 Kbytes per second. This means a little
less than 30 Mbytes per hour. The default of 230 Mbytes is therefore
enough for more than 8 hours per recording. A call that takes longer
continues in the next file, without loss of data.
SD Delete File after Sending
Normally, the files are kept on SD card and are not deleted by the
system, except when the maximum number of files is reached in
which case the oldest files are overwritten automatically.
It is an option to delete files after the content was sent to a Tunnel
server. A certain risk is taken then, because data cannot be recovered
anymore after deletion.
