RCA 301, Programmer'S Reference Manual, Page: 26 / 235

Sixteen-Magazine Retrieval Unit
681.6 Million Characters
Mnrfpl .1488-1 Filfi
R/W Station
Read/Write
Head
Assembly
\
D
8-10 ms —
Zone
Photocell
1 f
Model 3488-2
File Expansion Assembly
Magazines 0-7 Magazines 8-15
1 I I
Card (Feed) Transport Mechanism
<
«
Gate
Card (Return) Transport Mechanism
.Card Replacement
Entry Slot
Card Removal
•Dummy Magazine
Position
Figure 2
Card Format
Bands — Each 3488 card contains 128 tracks, each of which runs the full length of approximately 14.5 inches
of recording area on the card. The 128 tracks are divided into 64 separately addressable bands of 2 tracks each.
Characters are recorded bit-serial per track. Two tracks are recorded in parallel, each at a density of 700 bits per inch.
Blocks — Each band (two tracks) of recorded information is divided into 4 blocks of 650 7-bit characters each.
The capacity of the 3488-1 along with the expansion assembly are included below.
UNIT
Block
Band (4 Blocks)
Card (64 Bands)
Magazine (256 cards)
Retrieval Assembly (8 magazines)
Retrieval Assembly Plus Expansion Assembly (16 magazines)
NO. OF SEVEN BIT CHARACTERS
650
2600
166,400
42.6 million
340.8 million
681.6 million
Control
The Model 380 channel acts as the interface between a 301 Processor and up to four Model 3488 random access
units. Two Model 380 channels can be used in each 301 System.
The channel permits one-way transfer of data between one of four random access units and the 301 Processor.
The channel enables selection and reading/recording of magnetic cards contained in a random access unit, under
program control. Character parity checking and character buffering are performed in the channel.
The Control includes the addressing registers, decoding circuitry, necessary control interface, and buffering.
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