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MMD > Archives > March 1996 > 1996.03.02 > 02Prev  Next

Re: Scanning Recordo Rolls
By Wayne Stahnke

Hi, Steve! I am happy to make your acquaintance by e-mail.

The roll scanner I built is currently configured to accept any 11-1/4 inch wide, 9 port per inch roll (that is, any roll conforming to the American standard adopted early in this century). This includes early and late Ampico, Apollo, Artecho, Artrio-Angelus, early and late Duo-Art, "Green" (i.e. T-98) Welte-Mignon, Welte-Mignon Licensee, and others.

The scanner determines the location of each leading and trailing edge of each hole with very high accuracy, on the order of 0.1 mm. Since the punch advance of most rolls is on the order of 1.0 mm, the roll image contains a complete picture of the entire matrix of possible hole positions.

This is not just an academic or theoretical point. Accuracy of this sort is required for the following step in the roll reading process, namely reconstructing the master roll from which the production roll was made.
This is done by using the locations of the holes in the roll to calculate the locations of all possible punch positions. Each hole is near a punch position, displaced only by a small error due to the tolerances of the perforating process. Given the location of each punch position and the location of each hole, the punch position of each hole can be determined exactly.

A typical roll has a punch advance of about 1 mm, and is about 10 m long. Thus, there are approximately 10,000 punch positions along the length of the roll. Multiplying this by the 100 port positions, we see that a roll consists of a matrix of 100 x 10,000 hole positions (about 1,000,000 hole positions).

In other words, a roll is properly viewed as a PROM (Programmable Read-Only Memory) containing about 1,000,000 bits of information. The punch position along the length of the roll corresponds to the "address" of the (100-bit) "word" to be retrieved from the PROM. Once we have retrieved the contents of the roll, we have reconstructed the master roll from which the production roll was made. This master roll image can then be used to create an identical copy of the roll, completely without error.

If there are some Recordo rolls you have a particular interest in, send them to me and I will scan them for you. The resulting images are small (on the order of 50,000 bytes) and are easily transferred by attaching them as files to e-mail.

With best regards, I am

Wayne Stahnke

(Message sent Sat 2 Mar 1996, 18:40:40 GMT, from time zone GMT-0500.)

Key Words in Subject:  Recordo, Rolls, Scanning

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