BRG LK-4 cassette data storage

• can be connected to a (mini)computer as an external device for data input/output, data preparation or data media conversion
• can be connected directly to an electronic display or electronic typewriter for data transfer or modification purposes, or to a printer in standalone mode

The modified file can be (re)written to its original location or to another LK-4 (e.g. master data file supplemented with current salary data)

Structure

Major components

• Control circuits for performing writing and reading, tape movement, and data transfer
• Belt conveyor mechanics
• Interface lines:
  • 9 instruction traffic
  • 8 writing
  • 8 readbacks
  • 5 data traffic control and signaling
  • 9 output signals
  • 8 addressing

Operation

The data was recorded in blocks on the magnetic tape; block spacing approx. 32 mm

Recording mode: 2*¼ tracks (with stereo head), analog signal packets created with discrete frequency mixing pre-magnetization; block length:

• record read/write: 80 B
• for block read/write: n*80 B

The value of n is arbitrary; in the block running when the tape end signal appears, n _max =26

• average data rate: 140 Bps, maximum 4 kBps (max. 80 bytes)
• error rate: ≤ 10 ^-6 bits

Technical parameters:

• tape speed: 20 cm/s ± 1%
• cassette type: any COMPACT C
  • normal sound quality
  • 3.81 mm tape width
  • cassette capacity (C 90): 80-120 kB per page
  • Usability: at least 100 passes for any part of the tape
• fast winding (full rewind):
  • C60: kb. 100 s
  • C90: kb. 150 s
• power consumption: < 180 VA
• operating temperature: +10°C … +35°C
• operating relative humidity (excluding condensation): 20%…80%

Program set

Historical curiosities

After its approval in 1973, the LK-4 was included in the official external equipment set of the ESZR (EC 5094)

Resources

Journal of Communications, 1977/12, pages 371-374.

Video: SLK 4 data collection system (ITF Event, Oct. 30, 2013)