As data recovery from voice logging system becomes more widespread, we examine the history of voice logging systems.

Voice logging data recovery...

The necessity for the commercial logging of voice communications from telephone lines dates back to the early 1950's although there is evidence of patents for telephone answering and recording devices as early as 1903. The original commercial voice logging devices utilized analog magnetic tape as the recording media. The spools of 1/4” reel to reel tape were 10 1/2” in diameter and mounted on very large stable tape decks.

It is believed the earliest use for these cumbersome devices was used by both military and commercial logging of voice data for air traffic control. Although Magnasync Corporation were one of the early commercial manufactures of these devices the British company Racal became a market leader in voice logging. Racal Recorders designed and manufactured the voice logging systems and Racal Zonal the magnetic tape. Again these early magnetic tape voice logging systems utilized 1/4” magnetic tape on reel to reel spools. Both 1/2” and 1” tape was also used. These wider tapes allowed up to 64 simultaneous tracks of voice to be logged using analog recording techniques.

We have had three installments on RAID 5 failure and how the XOR operation gives us insight into discovering the stripe size and drive order for an array. Understanding the next installment is critical to the entire method of reverse engineering a RAID 5 configuration.

We understand that when we use an XOR operation on the same bits we always return FALSE. So, XORing a TRUE and a TRUE give you a FALSE, and XORing a FALSE and a FALSE give you a FALSE. Understanding this, we can hopefully understand the following.

The Master File Table (MFT) Magic number is ‘FILE’. Four ASCII letters represented in HEX format as 46h, 49h, 4Ch, 45h. These HEX values correspond to the letters ‘F’, ‘I’, ‘L’, ‘E’ respectively. Now, when you XOR 46h with 46h you get 00h. This is illustrated in the following diagram.

Figure 1