 | |
 | |
| Type | Punch card reader |
|---|---|
| Release date | 1965 |
| Predecessor | IBM 1402 |
| Related | IBM 2540 |
The IBM 2501 is a punched-card reader from IBM with models for the System/360 and System/370 mainframe systems and for the IBM System/360 Model 20, the IBM 1130 and IBM System/3 minicomputers. 2501 models can read 80-column cards at either 600 or 1000 cards per minute (CPM). [1]
The 2501 is no longer sold, but is simulated in software on current IBM systems. [2]
The 2501 comes in four models depending on speed and attachment features. Models for mainframe use come with an integrated control unit that performs the functions of a control unit required by other devices.
The A1 and A2 are for the IBM 1130. [3]
| Model | speed (CPM) | Integrated control unit? |
|---|---|---|
| A1 | 600 | no |
| A2 | 1000 | no |
| B1 | 600 | yes |
| B2 | 1000 | yes |
The 2501 uses a photoelectric sensor to read the data punched in the card. Cards are read serially (column by column) and the reader uses a simplified "straight through" card path. "Each column is read twice and the two readings are compared to check reading accuracy." [4]
In a mainframe environment the 2501 was frequently used for mainframe input in an "open shop" environment where users submitted their own jobs. [5] [6]
On an 1130 system the 2501 can be used in addition to the IBM 1442. Since the 1442 has a maximum speed of 300 or 400 CPM attaching a 2501 provides a significant increase in read speed and lower CPU usage.
The System/3 normally processes 96-column punched card; the 2501 provides alternative input for shops that require the ability to read 80-column cards.
A special feature (RPQ) is available for all models to allow them to read optically marked (OMR) cards. [7]
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