Microtape 555 Tape Transport / 550 Tape Control / Programs

This document, titled 'Microtape', serves as an informational and technical guide to the Microtape magnetic tape system, comprising the Type 555 dual tape transport and Type 550 tape control. The system is designed as a fast, reliable, and low-cost input/output and data updating facility.

Key features detailed in the document include:

• Fixed Position Addressing: Allows for selective updating of data without affecting adjacent information.
• Mechanical Efficiency: A simple transport mechanism without capstans, pressure pads, or mechanical buffering reduces wear.
• Bi-directional Operation: Reading, writing, and searching can be performed in either direction.
• Reliability: Employs redundant phase recording to minimize errors due to tape skew and amplitude variations.

The document provides comprehensive technical specifications for both the 555 transport and 550 control, as well as operational modes (Search, Read, Write, and Move). Additionally, it outlines the software support provided for PDP-1 and PDP-4 computers, including basic subroutines, maintenance/diagnostic programs (MICROTOG), and storage/retrieval software (MICROTRIEVE). The text also features detailed track formats, instruction lists, and operational flow charts.