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Single Channel Dual Clip Level

IP.com Disclosure Number: IPCOM000094912D
Original Publication Date: 1965-Jul-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Cassie, JV: AUTHOR [+4]

Abstract

The circuit produces two clipping levels at different times while reading tape. Normally, a high-clip level is signalled by gate 11 to all read sensing circuits. If an error is detected, a low-clip level is signalled during the next reread. Then, high-clip and low-clip levels are alternately used on following rereads.

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Single Channel Dual Clip Level

The circuit produces two clipping levels at different times while reading tape. Normally, a high-clip level is signalled by gate 11 to all read sensing circuits. If an error is detected, a low-clip level is signalled during the next reread. Then, high-clip and low-clip levels are alternately used on following rereads.

Binary trigger 10 normally is in reset status when no error occurs. In such status, trigger 10 activates an output condition from clip level gate 11 that causes high-clip operation by all detector sensing circuits when write input 16 is off.

If an error occurs while reading a tape block, a read error trigger, not shown, is set. In response to such trigger. the program causes a backspace call. And 12 is conditioned by the existence of a read error and a backspace call to set trigger 10. Then the trigger output conditions gate 11. This causes low-clip operation by the sensing circuits during the following reread pass of the tape block.

If the error persists after the second reading, the read error trigger is again actuated by another backspace call and read error to reverse the trigger output status. This reverses the condition of gate 11 to control a high-clip level during the next read pass. During subsequent rereadings due to persistence of an error, the clipping level alternates between low and high clip levels because of the operation of trigger 10.

Thus, an erroneous tape block can be read as many times as required...