The Three Card System:

The Three Card System is a method introduced by Ranganathan. In this system three different cards of the size 5" X 3" are maintained for each periodical. They are called the Register Card, the Check Card, and the Classified Index Card. Register Card: This is intended to  record information about the name of the periodical, the name of supplier, the periodicity, the order details, the  annual subscription,  the payment de-tails, details of issues received, etc. A specimen of the Register Card is given in Section 8.7. The Register Card enables the library to know the issues received and the dates of their receipt. These cards are arranged in a tray in alphabetical order so as to facilitate the title approach. Check Card: The Check Card is the most important contribution of this system. It contains columns for volume and number, due date, details of reminders, etc. It is the arrangement of these cards which meet its very purpose, namely, watching the receipt of the issues for acting upon when found overdue. A check card will be prepared for each of the periodicals ordered. These cards will then be arranged in a tray behind Guide Cards indicating the expected week of its receipt. There will be 60 week guides in all, as there can be a maximum of 5 weeks in a month. The guide cards will be numbered as follows:  

As and when a new issue of a periodical is received, its check card is located  from behind the appropriate Week Guide and information  is entered in  the columns. The Check Card  is then removed to behind  the Week Guide corresponding to its next issue. For example, the  current issue of  the periodical arrives in the library as expected in the second week of May. Its check card will be found in the set of cards behind the Week Guide numbered 5.2. After entering the  details, this card will be taken behind the Week Guide corresponding to its next issue. For example, the periodical is  a bi-monthly and therefore its  next issue is normally expected in the second week of July. The number of the Week Guide behind which the check card is to be refilled is 7.2. At the end of every current  week the check card remaining behind the corresponding Week Guide will be of those periodicals that have become overdue. The library can send reminders for them and do the necessary follow-up work. This is the great advantage of the check card. In fact, this has made the work of keeping track of the non-receipt of periodicals almost automatic.