Browse Prior Art Database

Magnetic Tape Sensing

IP.com Disclosure Number: IPCOM000074737D
Original Publication Date: 1971-Jun-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Beistle, RG: AUTHOR

Abstract

This differential detector senses the presence of magnetic tape 1 in threading channel 2 of a magnetic tape unit by two phototransistors 3' and 4, which are mounted in support 5 and detect reflected light.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 83% of the total text.

Page 1 of 2

Magnetic Tape Sensing

This differential detector senses the presence of magnetic tape 1 in threading channel 2 of a magnetic tape unit by two phototransistors 3' and 4, which are mounted in support 5 and detect reflected light.

An elongated light source 6 is mounted in support 5 and directs light across the threading channel toward reflective surface 7 carried by support 8. The space between these two supports defines the threading channel. The tape can occupy any position in this channel. Therefore, the intensity of the reflected light from surface 7 is less than the intensity of the reflected light from tape reflectors 9 or 10.

View B is a top view of support 5, showing tape 1 and a beginning of tape reflector 9 and an end of tape reflector 10 which are carried by the spaced ends of the tape.

The differential detector of View C includes two Schmitt triggers ST1 and ST2 which are sensitive to a relatively high input signal at terminals 11 and 12, respectively. Two other Schmitt triggers ST3 and ST4 are sensitive to only a lower input signal at these terminals. A constant current source connects the phototransistor emitters to the negative supply terminal.

When tape is not present, triggers ST1 and ST2 are turned off by the intermediate intensity light reflected from surface 7. When tape is present, none of the triggers are turned off by the low intensity light reflected from the tape. The relatively high intensity light reflected from tape reflectors 9 and 10 tu...