scope:

This specification covers the general requirements for power type variable resistors having a resistance element of wire, wound linearly on an insulating strip shaped in an arc, such that a contact bears uniformly on the resistance element when adjusted by a control shaft. The power ratings (see 3.1) cover a range from 6.25 watts to 1,000 watts, inclusive (see 6.2).

The PIN shall be in the following form and as specified (see 3.1):

The style is identified by the two letter symbol "RP" followed by a two digit number. The letters identify power type, wire-wound variable resistors and the number identifies the size and power rating.

The existence and location of an electrical off position at one end of the resistance element is indicated by a single digit, in accordance with table I. TABLE I. Electrical off position.

Symbol Electrical off position --------------------------------------------------------- 1 No electrical off position. 2 Electrical off position at end of rotation of control knob in a counterclockwise direction. 3 Electrical off position at end of rotation of control knob in a clockwise direction.

Beneficial comments (recommendations, additions, deletions) and any pertinent data which may be of use in improving this document should be addressed to: Commander, Defense Electronics Supply Center, ATTN: DESC-ES, 1507 Wilmington Pike, Dayton, OH by using the Standardization Document Improvement Proposal (DD Form 1426) appearing at the end of this document or by letter.

The style of shaft, type of mounting, and length of shaft is identified by two letter symbol. The first letter indicates the style of shaft and type of mounting and the second letter indicates the length of the shaft, in accordance with tables II and III, respectively.

The nominal resistance value expressed in ohms is identified by a three digit number; the first two digits represent significant figures and the last digit specifies the number of zeros to follow. When fractional value of an ohm, and values of less than 10 ohms are required, the letter "R" is substituted for one of the significant digits to represent the decimal point. When the letter "R" is used, the succeeding digit becomes significant. The following is an example: 3RO signifies that the resistance value is 3.0 ohms. The nominal total resistance values shall be as specified (see 3.1).

The resistance tolerance in percent is identified by two letters, in accordance with table IV. TABLE IV. Resistance tolerance.

Symbol Resistance tolerance -------------------------------------- KK Percent (±) 10

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