PUTTING SIMON TOGETHER
In order to put Simon together and make him work, not very much is needed. On the outside of Simon we shall need two small mechanisms for reading punched paper tape. Inside Simon, there will be about 50 relays and perhaps 100 feet of wire for connecting them. In addition to the 15 registers (I, S1 to S8, C1 to C5, and O), we shall need a register of 4 relays, which we shall call the program register. This register will store the successive instructions read off the program tape. We can call the 4 relays of this register P8, P4, P2, P1. For example, if the P8 and P2 relays are energized, the register holds 1010, and this is the program instruction that calls for the 8th plus 2nd, or 10th, register, which is C1.
For connecting receiving registers to the bus, we shall need a relay with 2 poles, one for the 2-line and one for the 1-line, for each register that can receive a number from the bus. For example, for entering the output register, we actually need only one 2-pole relay instead of the two 1-pole relays drawn for simplicity in [Fig. 5]. There will be 13 2-pole relays for this purpose, since only 13 registers receive numbers from the bus; registers I and C5 do not receive numbers from the bus. We call these 13 relays the entrance relays or E relays, since E is the initial letter of the word entrance.
Fig. 12. Select-Receiving-Register circuit.
The circuit for selecting and energizing the E relays is shown in [Fig. 12]. We call this circuit the Select-Receiving-Register circuit. For example, suppose that the P8 and P2 relays are energized. Then this circuit energizes the E10 relay. The E10 relay closes the contacts between the C1 relay coils and the bus; and so it connects the C1 register to receive the next number that is sent into the bus. This kind of circuit expresses a classification and is sometimes called a pyramid circuit since it spreads out like a pyramid. A similar pyramid circuit is used to select the sending register.
We shall need a relay for moving the input tape a step at a time. We shall call this relay the MI relay, for moving input tape. We also need a relay for moving the program tape a step at a time. We shall call this relay the MP relay for moving program tape. Here then is approximately the total number of relays required:
| Relays | Name | Number |
|---|---|---|
| I, S, C, O | Input, Storage, Computer, Output | 30 |
| P | Program | 4 |
| E | Entrance | 13 |
| MI | Move Input Tape | 1 |
| MP | Move Program Tape | 1 |
| Total | 49 |
A few more relays may be needed to provide more contacts or poles. For example, a single P1 relay will probably not have enough poles to meet all the need for its contacts.
Fig. 13. Latch relay.
Each cycle of the machine will be divided into 5 equal time intervals or times 1 to 5. The timing of the machine will be about as follows:
| Time | Action |
|---|---|
| 1 | Move program tape. |
| Move input tape if read out of in last cycle. | |
| 2 | Read program tape, determining the receiving register. |
| Read through the computing circuit setting up the C5 register. | |
| 3 | Move program tape. |
| Energize the E relay belonging to the receiving register. | |
| 4 | Read program tape again, determining the sending register. |
| 5 | Transfer information by reading through the |
| Select-Sending-Register circuit and the | |
| Select-Receiving-Register circuit. |
In order that information may remain in storage until wanted, register relays should hold their information until just before the next information is received. This can be accomplished by keeping current in their coils or in other ways. There is a type of relay called a latch relay, which is made with two coils and a latch. This type of relay has the property of staying or latching in either position until the opposite coil is impulsed ([see Fig. 13]). This type of relay would be especially good for the registers of Simon.
If any reader sets to work to construct Simon, and if questions arise, the author will be glad to try to answer them.
Chapter 4
COUNTING HOLES:
PUNCH-CARD CALCULATING MACHINES
When we think of counting, we usually think of saying softly to ourselves “one, two, three, four, ···.” This is a good way to find the total of a small group of objects. But when we have a large group of objects or a great many groups of objects to be counted, a much faster way of counting is needed. A very fast way of sorting and counting is punch-card calculating machinery. This is machinery which handles information expressed as holes in cards. Punch-card machines can:
- Sort, count, file, select, and copy information,
- Make comparisons, and choose according to instructions,
- Add, subtract, multiply, and divide,
- List information, and print totals.
For example, in a life insurance company, much routine handling of information about insurance policies is necessary:
Writing information on newly issued policies.
Setting up policy-history cards.
Making out notices of premiums due.
Making registers of policies in force, lapsed, died, etc., for purposes of valuation as required by law or good management.
Calculating and tabulating premium rates, dividend rates, reserve factors, etc.
Computing and tabulating expected and actual death rates; and much more.
All these operations can be done almost automatically by punch-card machines.