
                  ***  ACNET - Electronic Circuit Simulator   ***
                       ------------------------------------

 1.  INTRODUCTION
     ------------

 ACNET is an electronic circuit simulation program which calculates the
 steady state performance of circuits containing any combination of resistors,
 capacitors, inductors, transformers, transistors (bipolar & FET), op-amps,
 mutual inductors and thermionic valves.  The output shows the gain, phase
 shift, input and output impedances of the network at any given frequency and
 also provides gain plots over a wide frequency range.  The circuit values are
 stored on disk.  These may be modified at any time, extra components and nodes
 can be added or deleted, and input and output nodes redefined.  Comprehensive
 graph plotting facilities are also included using VGA graphics, supporting
 Epson (9 & 24 pin), IBM and HP DeskJet printers.  Fifty predefined frequency
 scales extending up to 300MHz over a range of 1, 2, 3 or 5 decades are
 provided together with the facility for a user defined frequency scale over
 any range.
 
 Two versions of the simulation program are supplied - a software only version
 and an extended version which gives better accuracy and which can use a
 coprocessor if available.  The program will run under DOS on any IBM 286 (or
 above) compatible PC with VGA graphics.  The full program requires 195KB of
 memory and preferably a hard disk.  The software may be installed from a
 supplied batch file and is easy to use from either the keyboard or by means
 of a mouse, with menus and helplines provided.  Program settings are stored
 and the same settings used on restarting.

 The program can be used to calculate the performance of any linear circuit,
 such as audio, video, i.f. and r.f. amplifiers, active and passive filters,
 matching networks, etc.  It can be used to evaluate the effectiveness of
 decoupling components and the stability criteria of oscillators.  Many circuit
 examples are provided, including simple filters, a transmission line, various
 feedback amplifiers, TV IF amplifier, a cascode circuit, a gyrator, a mutually
 coupled tuned circuit, a valve amplifier, Baxandall audio tone control and a
 9 band graphic equalizer.


 2.  INSTALLATION
     ------------
 
 Your supplied disk contains the following files :-

 1)   README.TXT     ...........  This documentation
 2)   ACNET.EXE      ...........  The circuit simulation program
 3)   ACNET_X.EXE    ...........  Extended circuit simulation program
 4)   ACNET.DEF      ...........  Defaults file used by simulation program
 5)   INSTALL.BAT    ...........  Installation program for Version 5.2
 6)   RESPONSE.EXE   ...........  Branch facility used by INSTALL 
 7)   CIRCUITS.TXT   ...........  Circuit schematics
 8)   HPFILTER.DAT    }
 9)   FBAMP.DAT       }
 10)  DUBTUNE.DAT     }
 11)  BANDPASS.DAT    }
 12)  NOTCH300.DAT    }
 13)  VALVEAMP.DAT    }
 14)  WHITEPNK.DAT    }
 15)  VIDEO1.DAT      }
 16)  VIDEO2.DAT      } ........  Sample datafiles for use with ACNET
 17)  RIAA.DAT        }                  Details in Section 7
 18)  CROSSOVR.DAT    }
 19)  LPACTFIL.DAT    }
 20)  NIC.DAT         }
 21)  BAX.DAT         }
 22)  GYRATOR.DAT     }
 23)  GRAPHEQ.DAT     }
 24)  TVIFAMP.DAT     }
 25)  LINE.DAT        }
 26)  WBAMP.DAT       }
 27)  GPRINT.BAT     ...........   Batch program for graph plotting
 28)  UNZIP.EXE      ...........   Decompression program for ZIP files
 29)  GRAPHE09.ZIP   ...........   Sample graphs for Epson 9 pin printers
 30)  GRAPHE24.ZIP   ...........   Sample graphs for Epson 24 pin printers
 31)  GRAPHIBM.ZIP   ...........   Sample graphs for IBM 24 pin printers
 32)  GRAPHHPK.ZIP   ...........   Sample graphs for Hewlett Packard printers
 
 The supplied files should be copied to your working disk - preferably a hard
 disk.  The installation program INSTALL.BAT will do this for you, creating
 the appropriate directories - \NET_V5 for the main files, with subdirectories
 \DATFILES and \GRFFILES for the data and graphfiles.  To install ACNET on
 drive C (for example), place a copy of the supplied disk in your input drive
 and set this as the current drive.  Then type :-

                             INSTALL  C:

 Any other valid drive may be designated for the installation.  Follow the 
 instructions and to save disk space only transfer the graphfiles that are
 suitable for your printer.


 3.  VERSIONS AVAILABLE
     ------------------

 Two versions of the program are supplied - ACNET.EXE and an extended version
 ACNET_X.EXE.  They are identical to the user and differ only in accuracy and
 speed.  ACNET is a software only version adequate for most purposes. 
 ACNET_X provides higher precision and range and consequently is slower.  If
 you have a coprocessor fitted to your machine this will automatically be used
 by the extended version giving about the same speed as the normal version.

 So if a coprocessor is available, always use the extended version ACNET_X.
 Without a coprocessor use ACNET for speed, especially for graph plotting.
 However, if you are using a very wide range of circuit values you may find
 that some results, (most especially the input impedance), are somewhat
 inaccurate due to matrix rounding errors.  Also, loading EMM386.EXE reduces 
 the speed of the extended version if a coprocessor is not present. 

 The programs supplied by the shareware vendors are limited to a maximum of 8
 nodes when calculating the circuit response.  You may obtain the full 50 node
 versions by registering with the author - see Section 10.


 4.  RUNNING THE CIRCUIT SIMULATOR
     -----------------------------

 To run, set the default directory to NET_V5 and type ACNET or ACNET_X for the
 extended version.  The screen (which is set for 80*25 characters) will show
 the program and system parameters and for ACNET_X confirmation of a co-
 processor if one is available.  Also the mouse will be activated if present -
 type <ESC> immediately on startup to disable the mouse if you wish.  All
 references to ACNET apply to both versions unless otherwise stated.  At the
 prompt press any key (mouse or keyboard) to continue.  The last used datafile
 will be selected automatically and the Main Menu will be displayed.

 The default settings as supplied will select the file HPFILTER for you when
 you first start.  This datafile contains values for a simple three element
 high pass passive filter (see CIRCUITS.TXT) and I suggest you use this
 initially to work through the menu options before defining your own circuits.
 The current revision number and a short message for the datafile will be
 displayed at the top of the screen.

 ACNET will run as a DOS based application from within Windows.  However it 
 should only be run full screen.  Use <ALT><TAB> to minimize the program.


 5.  THE MENU OPTIONS
     ----------------

 Select the option required either by using the keyboard up/down arrows or the
 mouse and then <ENTER> or by typing the appropriate letter on the menu line.
 Note that throughout the program, options that require a single character do
 not need a line terminator.  Typing ahead does not cause any problems as the
 input buffer is always cleared immediately prior to selection.  The mouse
 keys may be used for input - the left mouse key represents <ENTER> and the
 right key represents <Y> or <ESC> as appropriate.  When you have a multiple
 choice to make after the Main Menu, the options available will be displayed
 at the bottom of the screen.  The program name, version, name of datafile in
 use, the printer selected and the date will always be displayed at the top of
 the screen.  All the default settings are taken from the file ACNET.DEF and
 the values as supplied will suit HPFILTER.

 5.1  Display Component Values <D>
      ------------------------
 This starts by showing the number of nodes defined and the input, output and
 common node numbers.  Then all components, their allocated node numbers
 together with values and any further parameters will be displayed in an
 ordered sequence on the screen.  If the data exceeds the screen length then
 use the arrow keys or the mouse to view the complete list.  <ESC> returns you
 to the Main Menu.

 5.2  Print Component Values <P>
      ----------------------
 The circuit values etc. will be printed via LPT1: in the same format as
 appeared on the screen above.  As only text is involved any printer setting 
 may be used.  If the printer is off line, the program should prompt you to
 switch it on or to abort printing, although the actual response under these
 conditions is determined to a large extent by your printer setup.
 
 5.3  Response of Circuit <R>
      -------------------
 Supply the required frequency value in Hz.  Decimals may be used.  You may add
 <k>,<M> or <G> to represent kHz, MHz or GHz but there must be no gap between
 the last digit and the letter.  The response of the circuit at the given
 frequency will then be calculated and displayed showing :-

   (1)   Gain in decibels (dB).  A loss is indicated by a negative value.
         Max. value is 400dB and 50,000dB for the extended version.
   (2)   Phase Shift between the defined input and output nodes in degrees.  
         Values are only continuous in the range +180 to -180 degrees.
   (3)   Modulus of the Input Impedance in Ohms or multiples thereof.
   (4)   Modulus of the Output Impedance in Ohms.  If the real part of either
         impedance is negative this will be indicated.

 Repeat for other frequencies as required.  To obtain a printout, use the
 <PRINT SCREEN> key.  <ESC> will return you to the Main Menu.  Note that the
 mouse keys cannot be used to terminate numerical input.  ACNET will
 calculate the response of a circuit at zero frequency provided there is a DC
 path between the input and output - otherwise errors will occur.  E.g.,
 NOTCH300 has a finite response at zero frequency whereas HPFILTER does not.

 5.4  Change Component Values <C>
      -----------------------
 To input or to change existing component values the format is as follows :-

 COMPONENT       SYMBOL              PARAMETERS      [Optional value(s)]
 ---------       ------              ----------

 RESISTOR          R       Node_1   Node_2   Resistor Value (Ohms)

 CAPACITOR         C       Node_1   Node_2   Capacitance Value (Farads)

 INDUCTOR          L       Node_1   Node_2   Inductor Value (Henries) [R (Ohms)]

 MUTUAL INDUCTOR   M       Pri_S   Pri_F   Sec_S   Sec_F   Lp(H)   Ls(H)   k
                                                  [Rp(Ohms)]   [Rs(Ohms)]

 TRANSFORMER       T       Pri_S   Pri_F   Sec_S   Sec_F    Ratio (1:n)

 BIPOLAR           B       Base_node   Coll_node   Emitter_node   Beta   Ic(A)
 TRANSISTOR                         [Ft(Hz)]   [Cbc(F)]   [Cbe(F)]   [Cce(F)]

 FET               F       Gate_node   Drain_node   Source_node   Gm(A/V)
                                               [Cgd(F)]   [Cgs(F)]   [Cds(F)]

 VALVE             V       Grid_node   Anode_node   Cathode_node   Gm(A/V)
                                     Ra(Ohms)  [Cga(F)]   [Cgc(F)]   [Cac(F)]

 OP-AMP            A       I/P+  I/P-  O/P  [Gain(dB)]  [Zin(Ohms)]  [f3dB(Hz)]
                                 The Op-amp common is circuit common node.

 Values are typed in at the * prompt.  The usual component suffixes may be
 used ; i.e., p,n,u,m,k,M as appropriate.  For example, a capacitor of value
 6.8uF, an inductor of value 1.2mH with a series resistance of 0.1 Ohm and a
 resistor of 3.3kOhms all connected in parallel between nodes 3 & 4 would be
 input as :-
                      * C 3 4 6.8u<ENTER>
                      * L 3 4 1.2m 0.1<ENTER>
                      * R 3 4 3.3k<ENTER>       (or * R 3 4 3300<ENTER>)

 Definition of the series resistance of both inductors and mutual inductors
 (Rp, Rs) is optional - if undefined by the user then a value of 0.0001 Ohm
 will be assumed.  The value of the coupling coefficient (k) for mutual 
 inductors must be less than unity and will be set to a maximum value of 
 0.99999999999 if a higher value is used.  Similarly for transistor and valve
 capacitances which will be set to 1pF if undefined.  For bipolar transistors,
 Ft will be set to 300MHz, and for op-amps the default gain would be 80dB, the
 input resistance 10MOhms and the cut off frequency (-3dB) would be set to
 10MHz.  So a bipolar transistor (either NPN or PNP) with base connected to
 node 4, collector to node 7, emitter to node 9, with a current gain (Beta) of
 200 and a collector current of 1.5 mA would be input as :-

                    * B 4 7 9 200 1.5m<ENTER>

 The interelectrode capacitances would automatically be set to 1pF and Ft to
 300MHz.  However, if you wished to specify an Ft of 150MHz and capacitances of
 Cbc = 0.5pF, Cbe = 3.0pF and Cce = 10pF as well then this would be input as :-

                    * B 4 7 9 200 1.5m 150M 0.5p 3.0p 10p<ENTER>

 Components can be typed in any order.  If any component already exists, then
 its value will be changed to the latest value, which means that you cannot put
 components of the same type in parallel.  Note that delimiters must be spaces.
 The nodes for two terminal networks can be given in either order and the
 backspace key may be used to correct input.  Entering incorrect data will be
 indicated by a response of 'TYPING ERROR' and no change will take place.  The
 suffixes are not case sensitive except where there is ambiguity as in the
 above example - 'm' and 'M'.  You may not use inappropriate multipliers as the 
 range is restricted ; E.g. only 'm' for transistor current and only 'M' for Ft 
 will be used no matter whether upper or lower case is input.
 
 To delete a particular component type the symbol, the node numbers and then
 <D>.  E.g., to delete the above bipolar transistor you would type :-

                       * B 4 7 9 D<ENTER>

 On entering the 'Change' mode, the datafile revision number is automatically
 updated - this will appear on the graph and component printouts.  Having
 input/changed/deleted the values required, type <G> to go on.  If the datafile
 is a new one, you will be prompted to define the input, output and common
 nodes.  If an existing file was used then you may redefine these nodes if you
 wish.  This allows you to calculate the response of any intermediate part of a
 circuit - you may, for example, choose a decoupling arm as the input node in
 order to ascertain its effectiveness.  Note that the maximum node number is 50
 (8 for the smaller versions of the program) with no restriction on the number
 of components.  You cannot have an input/output/common node number greater 
 than the highest component node number defined.  If you ever have less than 3
 nodes then the program cannot calculate a result.

 5.5  Open a Data File <O>
      ----------------
 Component details are stored in datafiles with a .DAT extension.  The names of
 those already available will be displayed.  The current datafile may be closed
 and another opened by highlighting the file required using the up/down/left/
 right arrow keys or the mouse.  Use <F1> to create a new file (see below), 
 <F2> to make a copy with a new filename and <F3> to delete a datafile.

 5.5.1  Defining a New Circuit & Datafile
        ---------------------------------
 If you are starting with a new circuit, then you must number all the nodes
 (junctions) starting at 1 as shown in the example circuits.  It does not
 matter how you organize the numbers, but there should be no gaps in the
 sequence.  If you subsequently change the circuit and delete all connections
 to a node you must either reorganize the node numbers or you can leave the
 node unconnected - this will just slow down the analysis.  All common (ground)
 connections must have the same node number.  The power supply connections
 count as common, although you can allow for the supply source impedance.  Do
 not set main component values to zero otherwise errors may occur.  If you wish
 to join two nodes together without reorganising node numbers, use a small
 value resistor - say 0.1 Ohm.

 Having done this you must then create a new datafile.  Select 'Open Data 
 File' from Main Menu and then NEW_FILE by means of <F1>.  Type the name of
 the new file required - the .DAT extension will be added automatically.  You
 cannot type an illegal DOS filename.  The new file will be created and you
 will then be prompted to supply an appropriate header message of up to 45
 characters which will be displayed when you subsequently access the datafile.
 The revision no. of a new file will be set to 0.  You must then select the
 'Change Components' option in order to define the circuit values.

 5.6  Graph Plotting <G>
      --------------
 On selecting the graphplot facility, the Graph Menu will lead you to one of
 five further menus giving in total a choice from 49 preset frequency scales or
 a user defined scale.  Select the one you require by using the arrow keys or 
 the mouse.  You have a choice of frequency range as indicated, covering from
 0.003Hz up to 300MHz, over 1, 2, 3 or 5 decades.  Having made your selection
 of frequency scale, press <ENTER> to continue.  If you selected the user
 defined scale then you will first have to supply the start and finish
 frequencies required - on subsequent use of this scale new values may be
 defined or the previous frequency values can be reselected by using <ENTER>.
 Naturally the finish frequency must be greater than the start frequency.

 Once the graph plot calculation has been initiated, progress will be indicated
 by a horizontal bargraph.  You may abort and return to the Main Menu at any
 time by typing <ESC> ; there may be some delay with large circuits running on
 lesser PC's.  Having completed the calculations, the screen will show the
 Graphplot Range, which defines the frequency range employed and the maximum
 and minimum amplitude values computed over that frequency range. The Graphplot
 Menu shows the current graph parameters including the printer setting.  Set
 the printer as appropriate and optimize the graph plot settings to fit the
 range of the response to be plotted.  These parameters are :-

  1) Printer Selection   (1)   E09 - 9 pin Epson printers (FX80 standard).
     -----------------   (2)   E24 - 24 pin Epson printers (LQ400 standard).
                         (3)   IBM - IBM Proprinter (X24 standard).
                         (4)   HPK - Hewlett Packard (DeskJet 500 standard).
     Others printers will be be added if there is enough demand.

  2) Print Density    May be toggled ON/OFF by using the <ENTER> key.  Gives
     -------------    better print clarity if needed at the expense of speed.
     For the 24 pin Epson and IBM printers there is a third option of ENL to 
     enlarge the plot from 90 dpi to a pseudo 75 dpi to fill the paper area.

  3) Produce Printfile    Again this facility may be toggled ON/OFF by using
     -----------------    the <ENTER> key.  Useful on slower machines where
     you only wish to to display the response of a circuit.

  4) Graph Scale    Default initially 25dB.  Should be set to 5, 10, 15, 20,
     -----------    25, 30 .... etc., (i.e., any value divisible by 5) up to
     80.  Then in increments of 10 up to 150, and then in increments of 25 up
     to a maximum of 300.  These values represent the length of the Y axis of
     the graph in dB.  Incorrect values will be rounded down automatically.

  5) Top of Graph     Default initially +5dB.  May be set within limits of
     ------------     +300 to -300dB.  It is best to use multiples of 5 or 10.

  6) Superimpose Mode    You may superimpose plots.  If the Superimpose 
     ----------------    facility is enabled, you may clear the plot array at
     any time by toggling OFF/ON.  The array is cleared automatically if you
     change plot parameters.

  7) Continue    To continue with graphplotting (or press <ESC>).   
     --------

 On continuing, the response will be displayed on the screen.  Note that the
 calculated points (76 in total) are shown in green and are joined in white
 using a simple curve fitting routine.  Previous plots restored using the
 Superimpose facility are displayed in yellow.  Under conditions of extreme
 curvature (such as occurs in NOTCH300 and TVIFAMP), the curve plotting 
 can become badly conditioned and if this happens the intermediate values are
 computed and used instead.  This slows the plotting process somewhat which
 may become noticeable when plotting the response of large networks - however
 the improved results are well worthwhile.  After examining the displayed plot
 press any key when indicated to continue to the Print Menu which will show
 the current name of the graphfile and its size.  You may now obtain a print
 on the selected printer, rename the graphfile, save the graphfile, plot again
 (with different parameters perhaps) or return to the Main Menu.  If no
 graphfile was produced then only the last two options are available.  The
 graph data (if saved) will be stored in the subdirectory \GRFFILES using the
 data filename or a revised filename of your own choice, and will have the
 extension .E09 or .IBM or .E24 or .HPK as determined by the printer setting.
 You cannot change the extension when renaming the file.  Note that if you use
 an existing graph filename, subsequent saved files will overwrite the
 previous graphfile, but you will be warned that this is about to happen.

 On returning to the Main Menu you may then plot other graphs using an
 alternative frequency range or you may make component changes and plot more
 graphs using the Superimpose mode too if you wish - but obviously you cannot
 change either the frequency scale or the amplitude scale if you are wishing
 to superimpose plots.

 N.B.  Typing <ENTER> or an illegal character (e.g., a letter when a number is
       required) for any of the graphplot options will cause the default or the
       previously defined value to be used.  If you type an incorrect numeric
       value, this will not be accepted and you will be prompted for another
       value.  Also, if there are less than 3 nodes defined for the circuit the
       program will not run and you will be returned to the Main Menu.

 The default settings for the last datafile used, the graph parameters, the
 printer settings, etc. are contained in the file ACNET.DEF.  This is read
 every time you start the program and is updated whenever you make a change.
 The same defaults file is employed whichever version of ACNET is used.  If
 the defaults file becomes corrupted or even deleted, a new one with the
 original values will automatically be regenerated.

 5.7 DOS Shell <S>
     ---------
 Enables you to start a new DOS shell.  This facility assumes that COMSPEC
 has been defined, otherwise it will assume that COMMAND.COM is in the root
 directory (C:).  Type 'exit' to return to the Main Menu.

 5.8  Help Screen <H>
      -----------
 Displays this documentation.  The Help Menu allows you to find the topic of 
 interest.  Use Up/Down, PgUp/PgDn and Home/End keys or the mouse as before and
 <ESC> to quit.

 5.9  Quit <Q>
      ----
 This will close the current datafile and return you to DOS.

 N.B. In the unlikely event of not being able to return to the Main Menu, try
      <CTRL><C> then <CTRL><BREAK> to return to DOS ; if this fails then you
      will have to reboot.  Do not attempt this while the disk is being
      accessed in case files become corrupted.


 6.  GRAPH PRINTING FROM DOS
     -----------------------

 You will find that when you exit the simulator program the graphfiles saved
 will be in the GRFFILES directory with the appropriate file extension.  The
 graphfiles cannot be printed by using the DOS PRINT command as PRINT modifies
 certain characters.  This can be avoided by using the COPY command with
 redirection to the printer, which is already provided in GPRINT.BAT.  For
 example, from the NET_V5 directory you would use :-

                 COPY  GRFFILES\HPFILTER.E24  >  LPT1:     ... or
                 GPRINT  HPFILTER.E24

 Note that GPRINT automatically adds the path for you.  The graph points are
 calculated using an accurate logarithmic frequency scale.  The frequency
 range code is shown at the bottom of the graph preceded by '$' and followed
 by a '.' or ':' (indicating print density) and the graph file extension.


 7. SAMPLE DATAFILES
    ----------------

 The following datafiles are included.  Schematics for most of these are given
 in CIRCUITS.TXT and typical graphplots are included too.  Print out the
 appropriate graphplots to see what can be done.  The last six circuits contain
 more than 8 nodes and so the response of these can only be computed with the
 full 50 node version of ACNET.

 (1)  HPFILTER is a simple three element high pass filter with a cut off
      frequency (-3dB) of 299Hz.  The default graphplot settings suit this
      circuit well.  Use the Superimpose mode and change R 1 2 from 0.2 Ohm to
      1.0 and then 5.0 Ohms and note the changes in the response (as shown in
      the example graph).  Note that the inductor and its series resistance
      could have been combined into one circuit element.

 (2)  FBAMP is a simple two stage feedback amplifer with a gain of 30.5dB. The
      frequency response is 3dB down at 27Hz and 16.5kHz.  You can determine
      the feedback factor by opening the loop and noting the increase in gain.
      Note that R 2 5 is made up of 330k in parallel with 22k giving 20.625k.

 (3)  DUBTUNE is a mutually coupled double tuned circuit as would be employed
      in an i.f. amplifer.  The response with coupling factors (k) ranging
      from 0.03 (overcoupled) to 0.005 (undercoupled) are shown.  A coupling
      factor of 0.015 gives critical coupling - maximum bandwidth with a
      flat response.

 (4)  BANDPASS is a simple Butterworth active filter centred on 12MHz.  The
      circuit is taken from Electronics & Wireless World Dec 90, p1061.

 (5)  NOTCH300 is a high Q circuit tuned very accurately to 300.0Hz with a
      loss of exactly 100.0dB at the resonant frequency.  This circuit is 
      used for calibration.  As the notch is so sharp and deep you must ensure
      that any graphscale used has the 300Hz point accurately defined
      otherwise the full attenuation will not be apparent.

 (6)  VALVEAMP is a simple common cathode triode amplifier.  The bandwidth is
      extended by the addition of the 100uH inductor L 6 2.  N.B. u=gm*Ra.

 (7)  WHITEPNK is a filter to convert white noise to pink noise.  It has a
      slope approximating to -3dB/octave over the range 10Hz to 40kHz.  The
      circuit is taken from the Maplin magazine Electronics No.61 p53.  The
      author claims an accuracy of 0.25dB over the frequency range !

 (8)  VIDEO1&2 : VIDEO1 is a common emitter amplifier with a gain of 37.6dB
      and a bandwidth (-3dB) of 1.25MHz.  VIDEO2 is the same amplifier in a
      cascode arrangement - same gain with bandwidth increased to 3.85MHz.
 
 (9)  RIAA is a magnetic cartridge equalisation amplifier giving bass boost of
      20dB and treble cut of 20dB.  The response is accurate to within 0.2dB
      of the RIAA standard.

 (10)  CROSSOVR is a 3 way loudspeaker crossover network.  Crossover frequencies
       are 200Hz and 4kHz and the Superimpose mode can be used to plot the three
       individual responses on one graph.  By summing the three outputs you can
       obtain the combined response.  You will find that introducing a 180 deg.
       phase shift in the mid band output (equivalent to reversing the speaker
       polarity) gives the most level response.

 (11)  LPACTFIL is a low-pass active filter with Chebyshev response taken from
       Electronics World, Dec 95 p1088.  The response is within 0.01dB of the
       published figures in the cut off region.

 (12)  NIC is a negative impedance converter.  This circuit converts the 
       impedance Z 3 4 to its negative value at the input terminals.  Thus
       Zin at low frequencies is -10k and is -7.07kOhm in value at 10kHz 
       where the the capacitor reactance is 10k.  Two NICs together can be
       used to form an inverse impedance converter, better known as a gyrator.

 (13)  BAX is a Baxandall tone control circuit popular in audio amplifiers.
       This has a high impedance FET input stage.  The bass response is
       controlled by the potentiometer formed by R 15 16 & R 16 17 and the
       treble by R 10 11 & R 11 12.  To vary the response change the ratio of
       the resistors keeping the sum constant at 100k and 25kOhms respectively.
       The example graph plots show the response with the tone controls in
       various positions - the Superimpose mode was used to obtain these plots.
       The power supply impedance (R 1 2) is also included in this example.

 (14)  GYRATOR is a unity gain third order Butterworth filter with a 40kHz cut
       off frequency employing a gyrator.  Taken from Electronics World +
       Wireless World Jan 95, p54.

 (15)  GRAPHEQ is a nine band audio graphic equalizer based on circuits given
       in the NSC Audio/Radio Handbook.

 (16)  TVIFAMP is a 3 transistor TV IF amplifier with traps for sound and 
       chroma sub-carriers, used by Number One Systems Ltd. in their
       advertisements for their circuit analysis software.  ACNET gives
       results in good agreement with their published figures.  This is a good
       example of where a user defined frequency scale is needed as the
       amplifier covers such a restricted frequency range.

 (17)  LINE is a distributed LC line of 47 T sections with C=200pF & L=2uH
       correctly terminated with its characteristic impedance Zo of 100 Ohms.
       The output impedance Zout is zero at low frequencies but at 265948Hz,
       where the line is a quarter of a wavelength long, the phase shift is
       90 deg. and Zout reaches its first maximum.  At just above 1MHz the 
       phase shift reaches 360 degrees and Zout approaches zero as at this
       frequency the line is one wavelength long.  The input impedance Zin is
       always equal to 100 Ohms at any frequency (up to the cut off) whereas
       Zout varies with frequency as the driving end of the line is not matched.
       It is interesting to evaluate the line parameters at half and three
       quarters wavelength.  Above about 10MHz the simple equations are no
       longer accurate due to the finite number of sections and above 15MHz
       the line acts as a LP filter with very rapid attenuation.
 
       This circuit has the maximum of 50 nodes.  On a 25MHz 386SX (without
       coprocessor) the program takes 9 sec for each frequency calculation and
       48 sec for the extended version (without EMM386).  A 100 MHz Pentium
       takes 0.47 sec for both versions.  It is primarily the number of nodes
       - not the number of components - that determines the calculation time.

 (18)  WBAMP is a wideband differential amplifier.  Plots show the response with
       source impedances of 100 and 1k Ohms.  By joining the two inputs together
       you may calculate the common mode rejection - note how this degrades at
       the higher frequencies to be just visible on the plot.  (Circuit taken
       from The Art of Electronics by Horowitz and Hill, 2nd edition, p870).


 8. TESTING, RUNTIME ERRORS & HARDWARE REQUIREMENTS
    -----------------------------------------------

 ACNET is written in Borland Turbo Pascal (C) Ver 6.0.  Full error checking is
 on continuously as this does not slow the program appreciably.  Minimum
 hardware requirements for this latest version of the program are a 286
 compatible PC with VGA graphics, 195KB of memory and preferably a hard disk.
 Comprehensive testing has been carried out on a range of IBM compatible PCs
 running MSDOS 3.3, 5.0 & 6.2.  ACNET will run as a DOS based application from
 within both Windows 3.1 and Win95 provided the program is run full screen.
 However, in order to run ACNET with Win95 and DOS 7, the mouse must be 
 disabled (see Section 4).  There are no problems with earlier versions of DOS
 running with Win95.

 Comparison of the results obtained using PCSPICE to analyse some of the
 circuits shows exact agreement with ACNET.  The graph plot routines have been
 tested on an HP DeskJet 500 printer, on a Texan/Kaga KP-810 printer for the
 9 pin plots and on Epson LQ400, Star LC24-10 and Canon BJ-300 for the 24 pin
 variants.  The Star and the Canon printers were also used to emulate the IBM
 Proprinter.  Your Epson printer must support the graphics standard (up to and
 including ESC/P 81).  If your printer has a "stay in panel pitch" facility
 this should be set to OFF and the input buffer ON.  Note that some so called
 "Epson compatible" printers do not comply fully with the Epson standard.


 9.  CHANGE HISTORY
     -------------- 
 
 9.1.  Main Changes Incorporated in Version 2
       --------------------------------------
  1)  Easy to use menus provided, with no type ahead errors.
  2)  Graph plotting facilities considerably extended.
  3)  Provision of a defaults file which can be changed by the user.
  4)  The ability to use two disk drives if required.

 9.2.  Main Changes Incorporated in Version 3
       --------------------------------------
  1)  The use of predefined multilevel symbols for graph plotting.
  2)  Improved models for inductors, transistors and op-amps.
  3)  Printing capabilities include IBM and HP DeskJet printers. (V3.2)
  4)  All screen displays now provided by ACNET instead of LIST.COM. (V3.2)
  5)  Change of address for registration. (V3.2)

 9.3  Main Changes Incorporated in Version 4
      --------------------------------------
  1)  Use of suffixes k,M,G,T,m,u,n and p as component value and frequency
      multipliers.
  2)  Use of the mouse to control the program.
  3)  Addition of thermionic valves to the component menu.
  4)  Bug fix for HP printers (V4.2).
 
 9.4  Main Changes Incorporated in Version 5
      --------------------------------------
  1)  Use of VGA graphics giving a much improved screen display and printer 
      output.  Enlarged graphplots for 24 pin Epson and IBM printers (V5.2).
  2)  The ability to start another DOS shell from the program.

 9.5  Future Development
      ------------------
 It is planned to extend the graphplotting facilities for the current version
 in the near future.  Version 6 of the program (due to be completed in 1997)
 will incorporate the calculation of square wave and impulse response.


 10.  REGISTRATION
      ------------

 ACNET is issued as shareware.               Author - Peter M. Montgomery

          Address  -  Downings
                      Bells Hill              Telephone  -  01753 643384
                      Stoke Poges
                      SLOUGH  SL2 4EG   (UK)

 Advice, subsequent revisions and copies of the full program which can handle
 larger circuits with up to 50 nodes can be obtained by registering with the
 author for a fee of 10 pounds sterling plus 2 pounds for postage if overseas.
 When registering it would be helpful if you would indicate (i) the version of
 ACNET that you are currently using and (ii) your source of supply.


          ACNET : Version 5.20  Copyright (C) 1991-96  P.M. Montgomery
          ------------------------------------------------------------

                                              README(52).TXT         05/02/96
