Not long after the Group was founded in 1970 Joan Harding, our Founder, realised that it was essential to have a system for indexing the key facts which we note in our recordings. She sought advice from some information processing experts and they recommended that the DBRG should record such facts on Visiscan cards - familiarly known as 'Peek-a-boo' cards. At that time personal computers were still some years into the future
Each of these cards is 10 inches (25.5 cm) wide by 12 inches high ( 30 cm) and is subdivided into 10 columns of 10 rows, i.e. 100 segments. In turn each segment comprises 10 columns of 10 rows, giving a total of 10,000 individually numbered points on each card.
Each card was used to represent an architectural feature - such as a Smoke Hood - and a hole would be punched in the point which corresponded to the DBRG reference number of a building in which this feature had been noted. For example, Building reference 1324 is marked below in red in the large square in row 1 column 3, and therein on row 2 column 4.
The card thus identified every building in which a Smoke Hood had been observed.
Joan was very keen to discover buildings in which certain combinations of features had been noted. By picking out the cards for these features and holding them together against the light she could see where such combinations had been found.
This system was cumbersome to use because each punched hole had to be translated into a reference number and then looked up in a separate hand written index in order to identify the name of the building. Furthermore it could only be referred to at one site, and a 'back-up' copy would be quite impractical.