Do almost anything control system, using a computer
Twin track into single track point control that can be programed
Computer control is only as safe as the programmer's imagination

The relay type block control system meets the requirements for some kind of safe control of trains in blind and inaccessible places, this was 100% reliable but it was not quite flexible enough for more complicated manoeuvres like changing track at the opposite end of the single section. This was needed to allow the Beer DMU to enter the station at Book Tunnel then proceed to the goods yard, to keep main line clear. 
After a bit of thinking the sinclair computer was installed with a few interface circuits. This system can be easily modified for use with a modern pc

note
the drawing shows four inputs per joystick, but there were five. ie:- left, right, up, down and fire.
 

A sensor of some description is located at up to ten key positions around the layout, this makes all sorts of programmable train movements easily or otherwise accomplished. You can either sit back and watch or carry out operations on some other part of the railway.  


address 61438 (joysick port one) and address 63486 (joystick port two)


 
This is the sensor positions with relation to data for the IN or PEEK command of the spectrum. IN 63486 will give the data number corresponding to the sensor. No sensor input =data number 191 
sensor
bit
bin
data number
1
1
191,1
190
2
2
191,2
189
3
4
191,4
187
4
8
191,8
183
5
16
191,16
175
 
The sensor numbers are allso the same as the key board numbers, port two keys 1 to 5 and port one keys 6 to 0
Joy stick nine pin D plug
pin 1  nc 
pin 2  common 
pin 3  nc 
pin 4  orange/white 
pin 5  white/orange 
pin 6  blue/white 
pin 7  white/blue 
pin 8  white/green-common 
pin 9  green/white 
 
The PEEK command is only used for looking at internal address values and not much use in this case. The IN command returns the value of an address and can give the result of more than one value at the same time. ie sensor 1 returns 190, sensor 2 returns 189, both sensors on will return 188. One way to check sensor data is with this very simple program. (sinclair basic.)

10 PRINT IN 63486
90 GOTO 10

The numbers just scroll down the screen and change when sensors or keys are activated.Using this information it is quite straight forward to creat a control system once the I/O cards have been built.  

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I/O cards

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