Table 3.2: Equipment Item 10to2 PR-CB 2to10 Description Base-10 Card Reader *   * For reading base-10 cards. During a 2to10 conversion operation, while the CA is actually the source of the coefficient of interest, the Output 10 Conversion Card must be present in the base-10 reader. Base-10 Display     * Displays one base-10 number (unsigned). Base-2 Card Reader   * * For reading base-2 cards. Base-2 Card Punch * *   For punching base-2 cards. CA Memory Drum * * * Counter Abacus. Holds the coefficients of one equation. Main register for most operations. KA Memory Drum   *   Keyboard Abacus. Holds the coefficients of one equation. The second operand, or subtrahend for pair-combining.

Table 3.3: Controls Control Type 10to2 PR-CB 2to10 Description READER SELECT 2-pos. toggle up down up / down Must be set to the according base-2 or base-10 reader before read operations. IBM CARD READ 2-pos. toggle up down down Enables detection of the sign of the coefficients from the base-10 reader. ENABLE OUTPUT 10 2-pos. toggle down down up Enables the base-10 display. BANK six 2-pos. toggles up / down   down During a base-10 read operation, these switches select which one of six banks on CA will receive the 5 coefficients from the base-10 card. SIGN CHANGE plug & 30 jacks OFF 1-30 1-30 Selects which coefficient to eliminate during PR-CB operations, and which coefficient to convert during 2to10 operations. ZERO DETECT plug & 30 jacks OFF 1-30 1-30 These are used in a manner identical to the SIGN CHANGE plug and jacks. READ 10 push *   * Read contents of base-10 card, converted to base-2, into selected bank of CA. Also used to start a 2to10 conversion operation. CLEAR base-10 display push     * Clear the base-10 display. GO push   *   Perform pair-combining (elimination) operation. ADD/SUB push   * * Selects the initial add or subtract mode for PR-CB and 2to10 operations. For PR-CB, if the signs of the selected coefficient are the same on the CA and KA drums, the initial mode should be set to SUB; if they differ, to ADD. For 2to10, if the sign of the selected coefficient is positive, the initial mode should be set to SUB; if negative, to ADD. READ 2 push   * * Read contents of a base-2 card into CA. PUNCH 2 push * *   Punch contents of CA onto a base-2 card. TRANSFER CA TO KA push   *   Copy the contents of CA to KA. CLEAR CA push *     Clear the contents of CA. CLEAR KA push       Clear the contents of KA.

Table 3.4: Indicators Indicator 10to2 PR-CB 2to10 Description READ 10 *   * Base-10 card read in progress. ELIMINATING   *   Pair-combining in progress. OUTPUT 10     * Base-10 output (conversion) in progress. READ 2   * * Base-2 card read in progress. POSITIVE   * * Coefficient selected by the SIGN CHANGE plug is positive. When the SIGN CHANGE plug is moved, one must wait for a full revolution of the drums to be completed after the move (2 seconds, not 1 second) before the POSITIVE and NEGATIVE lamps are valid for the newly selected coefficient. NEGATIVE   * * Coefficient selected by the SIGN CHANGE plug is negative. ADD   * * Add mode selected. SUB   * * Subtract mode selected.