Manual which came with a Relay 153 Duplex slide rule. This manual also contained a catalogue of "Relay" bamboo rules which details the model number and the scales for each rule.

• Author: Not Stated
• Copyright Date: Not Stated
• Pages: 30
• Condition: Fair. The manual is worn and has a crease from being folded and stored in the box for many years.

This manual is available for download.

The Scales and Their Usages

Slide Rule Operation:

1	Multiplication
2	Continuous Multiplication
3	Division
4	Mixed Calculation of Multiplication and Division
5	The Folded Scale CF and DF
6	Squares and Square Roots
7	Cubes and Cube Roots
8	Reciprocal
9	Another Fundamental Calculation
10	The Sine of an Angle
11	The Cosine of an Angle
12	The Tangent of an Angle
13	The Sine and Tangent of an Angle Smaller than 5°54´
14	The Function of Angles Less than 0°34´
15	Other Trigonometrical Functions
16	Logarithms

Log Log Scales:

17	Multiplication
18	Continuous Multiplication
19	Division
20	Mixed Calculation of Multiplication and Division
21	The Folded Scale CF and DF

Duplex Slide Rule for Expert Electrical Engineer:

22	General Description
23	Arrangement and Usage of Scales
24	Trigonometrical Function
25	Vector
26	Hyperbolic Function
27	Hyperbolic Function of Complex Angle
28	Decibel Calculation
29	Some Applications on Electrical Problems

All of that in only 30 pages. Most of the sections are very brief and only briefly touch on some of the topics, many are just a single calculation or description of the usage and the user is expected to already have the basic understanding of what the author is describing.