IBM 610 Manual Of Operation

Also see for 610: Technical overview and introduction

34 IBM 6 10CR Turns the typewriter on and returns thecarriage.RO Causes the contents of register 14 to betyped out on the typewriter without signdue to type suppression. When it is de-sired to begin reading out the contentsof registers with their signs, read out(ro) must be preceded by a seq 01 todrop out the selector.A selector may be used without actually turningcontrol of the 610 over to the control panel. Supposewhen a SEQ 09 command is given, we wish to turnon the CLASS response 2; and when seq 10 is given,we wish to turn off class response 2. The class re-sponse 2 switch on the keyboard, must be set in thecontrol-panel position. The wiring is shown in Fig-ure 29.If the instruction seq 09 is given on the programtape, the selector is picked up and all subsequent class2 instructions will be effective. If the instructionseq 10 is given on the program tape, the selector isdropped out and all the subsequent class 2 instruc-tions will be ignored.The next instruction to the machine will comefrom the program tape and the program step hubsin no way affect the instruction pattern.Balance Test HubsAt the center of the control panel is a set of twelvebalance test selectors or switches. When any one ofthe registers of the machine is selected, electrical con-tact is estabHshed between the c hubs and the -(- or -hubs, depending upon whether the number storedin the register is positive or negative. This is accom-plished by a twelve-pole double-throw switch (re-lay) whose status is controlled by a sign-sensingcircuit. The relay will switch automatically from -|-to - and vice versa, according to the sign in the se-lected register.Zero is considered by the machine to be a positivenumber.In the event the selected register is positive, theconnections between c and -|- are shown in Figure 30.Note that all positions are connected simultane-ously.If the number in the selected register is negative,the connections between c and - are shown in Fig-ure 3 1.SELECTORSFigure 29. Balance Test HubsFurthermore, if the sign of the number in the se-lected register changes in the course of an operation,the state of the balance test relay changes corre-spondingly to follow this change of sign.The IBM 610 may be programmed to choose auto-matically one of several alternative procedures ac-cording to the result of an earlier part of the calcula-tion. This is what we mean when we speak of thelogical facilities of the 610.The balance test relay is the logical element mostfrequently used in conditional programming of thecomputer. It may be shown that any required logicaldecision may be reduced to a decision based upon thesign of a numerical quantity standing in one of theregisters.