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OOQQThe  Boston  Computer  Society 


SINCLAIR-TIMEX  USER  GROUP  NEWSLETTER 


Volume  2,  Issue  3 


March  1983 


This  newsletter  is  produced  to  inform  group  members  of  the  agenda  and 
logistics  for  future  meetings,  as  well  as  to  recap  and  amplify  the  information 
provided  at  the  last  meeting.  It  also  provides  a  forum  for  members  and 
interested  parties  to  communicate  what  they  have  learned  or  developed  relating 
to  Sinclair  and  Timex  computer  products. 


USER  GROUP  MEETINGS 

Date:  Wednesday,  March  16,  1983 

Time:  7:00  p.m. 

Place:  Large  Science  Auditorium,  UMass,  Harbor  Campus 

(Directions  on  last  page) 


At  this  meeting,  Larry  Becker  will  be  demonstrating  a  practical 
application  of  the  Sinclair-Timex  computer.  The  computer  is  used  as  an 
"intelligent  laboratory  station  terminal."  Specifically,  the  computer 
collects  analog  data  at  a  school  laboratory  work  station,  and  forwards  the 
data  to  a  centralize  computer.  The  complete  system  can  contain  up  to  16 
Sinclair-Timex  computers  and  a  central  Apple  computer.  Larry,  who  is  on  a 
sabbatical  leave  from  Siram  College  in  Northeast  Ohio,  is  developing  the 
system  at  the  Technical  Education  Research  Centers  (TERC)  in  Cambridge. 

Also  planned  for  the  March  meeting  is  a  review  of  the  E-Z  Key  keyboard  by 
Bob  Masters  and  a  review  of  MCODER,  an  integer  compiler,  by  Will  Stackman. 

Following  the  presentation,  we  want  to  break  up  into  groups  to  discuss 
topics  of  special  interest.  At  the  past  few  meetings,  we  have  had  little  time 
for  such  groups  —  a  situation  we  are  trying  to  correct.  Tentatively,  an 
advanced  and  beginner's  group  are  planned,  but  groups  to  discuss  the 
presentations  or  to  discuss  FORTH  can  be  formed,  depending  upon  interest  of 
those  attending  the  meeting. 

The  April  meeting  will  be  held  on  the  13th,  the  second  Wednesday  of  the 
month.  If  you  have  items  to  discuss  at  the  meeting  or  suggestions  for 
presentations,  contact  Sue  or  Cliff. 


NOTE  THE  CHANGE  OF  THE  APRIL  MEETING  DATE. 


HIGHLIGHTS  OF  THE  FEBRUARY  MEETING 

Sue  Mahoney  opened  the  meeting  with  a  report  of  a  visit  to  Sub  Oak,  New 
York,  in  Westchester  County.  The  public  library  in  that  community  has  an 
interesting  new  project  —  they  are  lending  TS-1000  computers.  You  can  borrow 
the  computer  for  one  week  with  a  library  card.  There  are  fines  for  overdue 
computers  and  there's  a  long  waiting  list. 


HIGHLIGHTS 


Concluded 


Mike  Coughlin  lead  a  discussion  on  the  use  of  FORTH  with  the  Sinclair- 
Timex  computers.  Mike  explained  that  FORTH  is  a  computer  language,  as  is 
BASIC,  only  FORTH's  not  as  easy  to  learn.  After  loading  the  FORTH  program, 
you  can  write  programs  in  the  FORTH  language.  Mike  described  the  concepts  of 
the  FORTH  language,  such  as  words,  the  dictionary,  reverse-Polish  notation, 
and  threaded  interpretation.  In  FORTH,  you  generate  words  instead  of 
statements.  Instead  of  being  stored  with  line  numbers  in  sequence,  words  are 
stored  in  a  dictionary.  Reverse-Polish  notation,  similar  to  that  used  in  some 
calculators,  manulipates  a  stack,  which  is  used  to  store  numbers  like 
variables  do  in  BASIC.  When  a  program  is  run,  words  from  the  dictionary  are 
interpreted  following  the  logical  thread  defined  by  the  programmer. 

Mike  said  that  the  language  is  likely  to  be  used  more  in  the  future 
because  of  its  power  and  speed.  FORTH  is  useful  in  control  and  interfacing 
applications.  FORTH  programs  are  reported  to  run  as  fast  in  the  Slow  mode  as 
BASIC  programs  do  in  Fast  mode.  Mike  has  ZX  FORTH  from  Gladstone  Electronics 
(reviewed  below).  During  the  discussions,  Bob  Smith  stated  that  another 
version  of  ZX  FORTH  was  available  from  The  FORTH  Dimension,  a  company  in 
Pennsylvania.  There  are  differences  between  the  two  versions,  such  as  in  the 
use  of  the  Sinclair,  versus  ASCII,  character  set. 

Following  Mike's  presentation,  John  Kemeny  demonstrated  the  video  monitor 
interface  he  purchased  from  Random  Access,  Box  4177,  Phoenix,  Arizona  85080. 
He  previously  reported  that  his  computer  didn't  work  after  he  installed  the 
interface.  His  problem  proved  to  be  a  simple  soldering  error.  He  correctly 
soldered  the  resistors,  diodes,  transistors,  and  other  delicate  electronic 
components;  however,  in  the  output  connector,  he  shorted  the  two  connectors  of 
the  coaxial  cable.  This  was  quickly  fixed  once  the  error  was  found.  He  is 
now  very  happy  with  the  interface.  The  interface  costs  $20.45  postpaid  and 
provides  both  a  television  and  a  video  monitor  interface,  with  switchable 
normal  and  inverted  (white  on  black)  display.  John  also  discussed  why  one 
would  want  to  use  a  video  monitor  and  the  criteria  he  used  in  selecting  his 
monitor  (see  page  7). 

Peter  Nichols  gave  a  demonstration  of  the  Byte-Back  modem.  With  a  modem, 
it  is  possible  to  use  the  computer  and  a  telephone  to  communicate  with 
bulletin  boards  and  information  services,  such  as  the  Source.  The  Byte-Back 
modem  runs  nrt  300  baud  and  comes  with  software  to  allow  the  Sinclair-Timex  to 
emulate  a  "dumb"  terminal. 


REVIEW  OF  ZX  FORTH  FROM  GLADSTONE  by  Michael  Coughlin 

A  complete  new  programming  language  has  become  available  for  the  ZX-81 
and  TS-1000  computers  with  16  K  memory.  Called  ZX  FORTH,  it  promises  to 
become  an  increasingly  important  language  since  it  allows  the  very  small, 
computers  to  cope  with  complicated  applications.  Originally  developed  in 
England  by  Artie  Computing  Ltd.,  and  sold  through  Gladstone  Electronics  in 
Buffalo,  New  York,  ZX  FORTH  is  an  adaption  of  FigFORTH.  FigFORTH  has  a  good 
selection  of  instruction  manuals  and  system  expansions  supporting  it. 
Unfortunately,  this  first  edition  of  the  language  for  our  computer  suffers 
from  a  small  manual  with  many  errors.  Nevertheless,  the  language  is  so 
powerful  that  experienced  software  hackers  should  buy  ZX  FORTH  at  once. 
Beginners  are  advised  to  wait  until  better  instructional  materials  are 
provided  and  any  bugs  in  the  code  have  been  exterminated.  The  price  for 
ZXF0RTH  is  $29.95  plus  shipping. 


REVIEW  OF  THE  ORGANIZER  FROM  TIMEX  by  Jack  Hodgson 


"The  Organizer",  from  Timex,  is  a  data  base  management  program.  It  helps 
the  user  create,  maintain,  and  work  with  a  small  data  file.  It  may  be  easier 
to  think  of  this  program  as  a  box  of  blank  file  cards  onto  which  you  can  write 
all  sorts  of  information.  The  Organizer  helps  you  put  stuff  on  these  cards, 
alter  and  update  them,  sort  the  cards,  and  search  through  them  for  certain 
items . 

When  you  first  run  the  program,  you  are  asked  to  set  up  the  titles  for 
the  f iek*.  These  are  the  labels  that  will  appear  on  all  the  cards  in  your 
file.  Next  you  must  tell  the  program  where  each  "field"  is  to  begin.  The 
fields  are  the  areas  into  which  you  will  enter  actual  information  of  the  file. 

Finally,  the  program  shows  you  a  card  (actually  known  as  a  record)  that  has 
on  it  the  titles  you  entered  earlier,  onto  which  you  can  now  type  your  data. 

After  you've  entered  a  few  (or  more)  records  you  can  begin  to  work  with 
the  file.  Left  to  its  own  devices  the  program  will  put  the  file  in  order  by 
the  first  field  on  the  screen,  but  this  can  be  changed  easily  so  that  they  are 
ordered  by  any  field  you  choose.  This  is  done  with  the  command  ORDER. 

You  move  through  the  file  by  using  the  commands  FORWARD,  BACK,  and  LIST. 
The  first  two  will  step  you  through  the  file  one  record  at  a  time,  and  the 
latter  causes  the  records  to  appear  one  at  a  time  for  a  few  seconds  each  until 
you  stop  the  listing  by  pressing  a  key.  RESET  will  take  you  from  whereever 
you  are  in  the  file  back  to  the  first  record  in  one  step. 

ALTER,  DELETE,  and  ENTER  allow  you  to  alter  a  record,  completely  delte  a 
record,  or  add  new  ones,  respectively.  SELECT  is  the  most  powerful  and 
handiest  command  in  the  repertoire.  With  it  you  can  have  the  program  look 
through  all  the  records  for  any  words,  word,  or  even  a  few  letters  that  may 
exist  in  the  file.  The  program  will  display,  one  at  a  time,  all  the  records 

in  which  the  string  in  question  appears.  Because  I  don't  own  a  printer  I'm 

not  real  familiar  with  the  commands  that  access  it.  But  evidently  PRINT  and 
COPY  allow  you  to  print  a  copy  of  all  the  records  in  the  file  or  of  any 
individual  record.  Finally  INFORM  tells  you  how  many  records  you  currently 
have  and  how  much  space  is  left,  and  QUIT  takes  you  back  to  the  main  menu. 

Of  all  the  TS  produced  software  I've  seen  this  one  is  the  handiest 

(Vu-Calc  a  close  second).  The  documentation  is  relatively  adequate  but,  as 
usual,  printed  in  ludicrously  small  type.  The  on-screen  prompts  are  good  in 
that  all  the  directions  are  there  but  bad  in  that  you  must  read  them 
carefully.  Their  syntax  is  stilted  (to  my  eye)  and  they  are  inconsistent  in 
the  way  each  command  is  manipulated  (sometimes  you  move  the  cursor  around  with 
the  arrows  and  other  times  with  the  shift  key,  sometimes  you  exit  the  command 
with  the  enter  key  and  other  times  with  stop).  But  the  instructions  are  all 
there  on  the  screen,  you  just  have  to  be  sure  to  read  them  carefully. 

My  biggest  problem  with  this  program  is  its  small  capacity  (a  little  over 
9000  characters  for  data).  Of  course  this  is  really  limited  by  the  capacity 
of  the  machine  and  the  speed  of  the  load  routine  (It  takes  7  plus  minutes  to 
load  the  filled  to  capacity  file)  not  the  program  itself.  For  most  home 
applications  that  I  can  think  of  it's  perfectly  adequate. 


Also  included  on  the  cassette  is  a  copy  of  the  organizer  filled  with 
information  from  a  world  atlas.  "The  Gazeteer" ,  while  of  somewhat  dubious 
value  as  a  resource,  is  a  good  example  of  what  can  be  done  with  the  program. 


FRESH  SQUEEZED  COMPUTER  DATA 


Since  the  Sinclair-Timex,  and  many  other  computers,  store  characters  in 
8-bit  bytes,  it  is  commonly  assumed  that  8  bits  are  required  to  store  a 
character  of  text.  This  is  not  so.  There  are  methods,  called  data 
compression  techniques,  which  allow  you  to  store  data  in  less  storage  space. 
The  penalty  is  that  it  takes  time  to  encode  and  decode  your  data. 

The  amount  of  data  compression  that  can  be  achieved  depends  on  the  amount 
of  a  priori  information  known  about  the  data.  For  example,  in  English  text, 
the  letter  E  occurs  far  more  frequently  that  any  other  letter.  Therefore,  you 
could  save  space  by  using  variable  length  codes  with  short  codes  for  the 
letter  E  and  other  frequently  used  characters.  In  this  article  we  will 
examine  a  method  of  data  compression  which  does  not  make  assumptions  about  the 
frequency  of  use  of  characters. 

Information  theory,  a  field  pioneered  by  Claude  E.  Shannon  in  1949,  tells 
us  that  if  we  have  r  characters  to  choose  from,  then  at  least  log£  r  are 

required  to  store  a  character.  From  the  Sinclair-Timex  user's  manuals,  we  see 
that  there  are  approximately  256  different  characters  (a  few  are  not 
assigned),  with  CODEs  from  0  to  255.  Thus,  log^  256  =  8  bits  are  required  to 
store  an  arbritary  character. 

Does  this  contradict  with  what  we  said  earlier?  Not  if  you  note  that 
most  data  uses  only  a  small  fraction  of  those  256  characters.  Let's  consider 
text  which  uses:  the  digits  0  through  9;  the  three  punctuation  points  — 
period,  comma,  and  question  mark;  the  letters  A  through  Z;  and  the  space 
character.  The  minimum  storage  for  text  containing  just  these  40  characters 
is  log,.  40  or  approximately  5.3  bits.  If  we  were  able  to  pack  the  characters 
into  their  minimum  required  storage  space,  we  could  save  almost  3  bits  per 
character.  But  we  have  two  problems.  Firstly,  we  can't  store  data  in  a 
fraction  of  a  bit.  And,  if  we  use  6  bits  for  each  character,  we  wastes  about 
13  percent  of  the  storage  space  (what  a  different  a  bit  makes).  The  second 
problem  is  that  it  is  very  inconvenient  to  manipulate  6  bits  of  data  on  our 
computer,  even  in  machine  language.  The  solution  lies  in  bunching  characters 
together.  Three  characters  require  3*5.3  or  approximately  15.9  bits.  Using 
16  bits  for  three  characters  doesn't  waste  much  space. 

Following  is  a  very  flexible,  and  therefore  fairly  complex,  program  to  do 
data  compression.  You  may  have  difficutly  figuring  out  how  it  works,  thus  it 
is  probably  best  to  treat  it  as  a  black  box  —  us* it  as  is. 

•  M$  is  the  character  set,  which  in  our  example  is  the  40  characters  cited 
above.  You  could  replace  these  characters  with  those  characters  you  need 
in  your  application,  e.g.,  just  the  10  decimal  numbers. 

•  B  is  the  number  of  bytes  that  receive  one  bunch  of  characters.  Here  we 
are  packing  3  characters  into  two  bytes,  so  B  is  2.  The  program  figures 
out  N,  the  number  of  characters  to  pack  into  the  B  bytes,  in  this  case 
three.  You  can  find  the  percent  efficiency  of  your  packing  by  PRINTing 
100*(N*LN  M)/(8*B*LN  2),  where  M  is  LEN  M$. 

•  1$  is  the  input  characters  (your  data). 

•  The  subroutine  at  line  200  compresses  1$  and  returns  the  result  in  A$. 

If  the  number  of  characters  in  1$  is  not  a  multiple  of  N,  the  subroutine 
will  pad  1$  with  the  necessary  extra  character(s) . 

•  The  subroutine  at  line  800  decompresses  1$  and  puts  the  result  in  A$. 


Each  half  of  the  program  will  run  in  1  K  RAM,  if  the  REMs  are  deleted. 
(This  may  not  be  too  useful,  however,  since  there  is  little  room  left  for 
data.)  To  run  in  a  1  K  system: 

1.  Write  two  programs  —  one  with  the  compress  and  one  with  the 
decompress  subroutines. 

2.  Figure  out  what  your  data  encodes  into  using  compress. 

3.  Add  this  data  string  and  the  decompress  subroutine  to  your  final 
program. 


If  you  are  familiar  with  the  PDP-11  computers,  you  probably  have  seen 


this  compression  technique  under  the  name 
8),  50  is  decimal  40. 

1  REM  SQUEEZE 

2  LET  B=2 

3  LET  M$="1234567890  ABCDEFGH 
IJKLMNOPQRSTUVWXYZ , . ?" 

10  DIM  K(B) 

20  LET  T=256 
30  LET  M=LEN  M$ 

40  LET  N=INT  (8*B*LN  2/LN  M) 
100  INPUT  1$ 

110  GOSUB  200 

120  FOR  1=1  TO  LEN  A$ 

130  PRINT  I; "=" ;A$(I) ;C0DE  A$(I 

)>  £.  , 

140  NEXT  I  -  j 

150  STOP 

200  REM 
210  LET  A$="" 

220  IF  LEN  I$=N*INT  (LEN  I$/N) 

THEN  GOTO  250 

230  LET  I$=I$+M$(M) 

240  GOTO  220 
250  LET  1=0 

260  IF  ION*INT(I/N)  THEN  GOTO 
300 

270  Fm  K=B  TO  1  STEP  -1 

275  IF  I>0  THEN  LET  A$=A$+CHR$ 

K(K) 

280  LET  K(K)=0 
290  NEXT  K 
300  LET  1=1+1 

310  IF  I>LEN  1$  THEN  RETURN 
320  LET  J=-l 
330  LET  J=J+1 

340  IF  J+1<M  AND  I$(I)OM$(J+l) 

THEN  GOTO  330 

350  FOR  K=1  TO  B 

360  LET  K(K)=M*K(K)+J 

370  LET  J=INT  (K(K)/T) 

380  LET  K(K)=K(K)-T*J 
390  NEXT  K 


RADIX-50.  Why  50?  In  octal  (base 


800  REM  DECOMPRESS 
810  LET  A$="" 

820  LET  1=0 
830  LET  I=I+B 

840  IF  I>LEN  1$  THEN  RETURN 

850  FOR  K=1  TO  B 

860  LET  K(K)=C0DE  I$(I+1-K) 

870  NEXT  K 
880  FOR  J=1  TO  N 
890  LET  R=0 

900  FOR  K=B  TO  1  STEP  -1 
910  LET  R=K(K)+T*R 
920  LET  K(K)=INT  (R/M) 

930  LET  R=R-M*K(K) 

940  NEXT  K 

950  LET  A$=M$ (R+l )+A$ 

960  NEXT  J 

970  LET  A$=A$(N+1  TO  )+A$(  TO  N 
)  ~  “ 
980  GOTO  830 


400  GOTO  260 


RAM-PACK  WOBBLE 


RAM-pack  wobble  is  a  phrase  that  has  been  used  to  describe  a  problem 
frequently  encountered  with  the  Sinclair-Timex  computer  with  a  16-K  RAM  pack. 
(We  borrowed  the  phrase  from  Tim  Hartnell,  the  British  author  and  publisher 
who  spoke  at  our  December  meeting.  Tim  uses  the  phrase  as  the  title  of  a 
column  he  writes  in  a  British  magazine.)  The  problem  is  usually  observed  when 
entering  information  into  the  machine  and  results  in  a  system  crash.  It 
occurs  because  of  the  mechanical  design  of  the  RAM  pack  (reportedly  the  design 
is  that  of  Uncle  Clive  s  brother).  The  RAM  pack  is  cantilevered  off  the  back 
of  the  computer  such  that  motion  of  the  RAM  pack  relative  to  the  computer 
occurs  when  keys  are  pressed.  The  motion  causes  a  break  in  electrical  contact 
on  the  edge  connector  between  the  two  units. 

There  are  many,  many  different  solutions  to  the  RAM-pack  wobble  problem.  If 
you  have  had  the  computer  for  a  while,  you  have  undoubtedly  found  a  solution. 
For  new  users,  here  is  a  list  of  some  of  the  solutions  which  have  been 
proposed.  They  are  in  no  particular  order,  and  we  don't  guarantee  any  of  them. 

•  Tim  Hartnell  s  solution,  as  we  reported  in  the  January  newsletter,  is  to 
mount  the  computer  and  RAM  pack  to  a  shelf  with  big  C-clamps  and  to  use 
an  external  keyboard.  There  are  a  number  of  alternatives  associated  with 
the  use  of  an  external  keyboard  as  to  where  the  computer  is  placed  (e.g., 
on  the  shelf ,  in  the  base  of  the  keyboard) •  These  solutions  work  because 
they  eliminate  the  need  to  touch  the  computer. 

•  Will  Stackman,  in  the  missive  he  handed  out  at  the  last  meeting,  proposed 
Blue  Goo  as  "a  cheap  and  final  solution”  to  the  problem.  He  says  to  buy 
a  package  of  Fun-Tak  synthetic  rubber  kneadable  adhesive  at  your  local 
five  and  dime.  ”Wedge  a  wad  between  the  RAM  pack  and  the  case.”  Various 
other  solutions  using  household  and  silly  puddy  have  been  proposed,  but 
this  solution  is  perhaps  better  as  there  is  little  oil  is  the  Blue  Goo. 

•  Similar  to  the  Blue  Goo  solution,  the  use  of  Velcro  has  been  proposed  by 
several  different  people.  Simply  glue  a  strip  to  both  the  computer  and 
the  RAM  pack  and  the  wobble  is  gone.  Memotech's  memory  modules  come  with 
patches  of  self-adhesive  Velcro. 

•  0ne  of  frequently  cited  and  simpliest  solutions  is  to  pull  the  RAM 

pack  out  a  small  amount.  This  solution  doesn't  require  items  you  may  not 
have  in  the  house.  Some  have  suggested  the  reverse,  pushing  the  RAM  pack 
in  as  far  as  it  will  go;  however,  pulling  out  a  silly  millimeter  or  two 
is  probably  the  more  reliable  solution. 

•  More  than  one  person  has  soldered  the  RAM  pack  to  the  edge  connector. 

Less  drastic,  but  equally  effective,  ribbon  cable  can  be  soldered  to  both 
units  providing  a  permament  connection.  It  has  also  been  suggested  that 
the  edge  connector  be  replaced  with  a  more  reliable  connector. 

•  Various  arrangements  of  elastics  have  proved  effective.  Gene  Blumenreich 
says  to  wrap  three  large  rubber  bands,  of  the  type  found  on  the  Boston 
Sunday  Globe,  around  the  base  of  the  computer  and  RAM  pack.  Be  sure  to 
place  the  rubber  bands  so  they  don't  go  over  the  keyboard.  Place  a  book 
or  magazine  under  the  computer,  but  not  the  RAM  pack.  Don't  let  anything 
hit  the  RAM  pack.  Gene  writes  that  "the  resulting  structure  looks  messy, 
but  it  is  pretty  stable." 


MORE  RAM-PACK  WOBBLE  SOLUTIONS 


One  company  is  selling  a  flexible  cable  interface  between  the  computer 
and  RAM  pack.  Another  company  manufactures  a  plastic  guard  which 
surrounds  the  RAM  pack  to  prevent  bumping  of  the  unit. 

•  Wedging  erasers  and  pencils  between  the  computer  and  the  RAM  pack  have 
been  proposed.  The  use  of  contact  cleaner  and  television  tuner  lubricant 
have  apparently  been  used  by  some  people  to  good  effect.  It  has  been 
suggested  that  the  use  of  a  soft  surface  for  the  computer,  such  as  a 
magazine  instead  of  a  table,  will  prevent  wobble. 

•  Finally,  Your  editor  has  a  4-inch  printed  circuit  board,  with  appropriate 
edge  connectors  on  each  end,  to  separate  the  computer  and  RAM  pack.  In 
addition  to  solving  the  wobble  problem,  this  allows  access  to  the  edge 
connector  signals  required  by  other  peripherals. 

YOU'VE  GO  THE  LOOK 

One  of  the  terrific  things  about  using  a  Sinclair-Timex  computer  is  that 
it  is  so  educational.  And  you  can  learn  about  more  than  just  BASIC.  For 
example,  recently  a  friend  of  mine,  John  Rommelfanger ,  demonstrated  a  MicroAce 
(an  obsolete  ZX-80  copy)  connected  to  a  video  monitor.  Instantly  I  knew  I 
wanted  a  monitor.  The  reason  is  very  simple  —  I  liked  the  look.  Although 
I  ve  read  about  using  a  UHF  modulator,  and  other  ways  to  clean  up  the 
television  picture,  there  is  really  no  beter  way  to  eliminate  eye  strain  than 
a  monitor. 

With  the  help  of  John  and  others,  I  quickly  learned  all  about  what  to 
look  for  when  selecting  a  monitor.  Here's  the  poop. 

First,  decide  if  you  will  use  the  monitor  just  with  the  Sinclair-Timex, 
or  with  other,  future,  computers  (the  TS-1000000,  perhaps).  The  most 
important  feature  of  any  monitor  is  its  bandwidth,  which  is  measured  in 
megahertz  (MHz).  It  determines  the  maximum  resolution  (or  fineness)  of  the 
picture.  A  television  has  a  maximum  of  4  1/2  MHz  bandwidth,  while  inexpensive 
monitors  range  from  8-22  MHz.  Price  is  almost  directly  proportional  to  the 
bandwidth  —  cheaper  monitors  have  less.  Because  the  Sinclair-Timex  produces 
a  low  resolution  picture,  it  will  look  virtually  the  same  on  any  monitor. 

Second,  check  the  phosphor.  They  come  not  just  in  black  and  white,  but 
also  in  green  and  amber.  Europeans  use  amber  almost  exclusively.  It  is  very 
nice,  but  there  is  a  slight  premium  on  it  in  this  country.  Also,  the  phosphor 
speed  is  important  —  get  P31,  a  fast  phosphor  (don't  let  the  salesman 
convince  you  that  slow  phosphors  will  reduce  flicker). 

Third,  check  the  input  jacks.  Most  monitors  have  75  ohms  impedance 
input.  Some  also  have  a  high  impedance.  If  you  plan  to  directly  connect  the 
wire  going  into  the  computers  modulator  (the  little  silver  box  inside)  to  the 
jack,  you  should  use  the  high  impedance  or  build  a  one  transitor 
emitter-follower  circuit.  Some  people  have  had  success  without  either 
however.  In  any  case,  I  remmend  you  build  a  video  inverter  circuit,  because 
light  on  dark  looks  far  better  on  a  monitor.  Some  monitors  come  with  a  nylon 
antiglare  screen.  These  reduce  the  brightness  slightly,  but  enhance  the 

contrast.  These  screens  can  be  purchased  separately,  but  they  tend  to  be 
expensive. 

Finally,  check  to  see  if  the  monitor  has  a  handle.  This  is  often 
overlooked,  but  much  appreciated  when  the  monitor  has  to  be  moved. 


/ 


GENERAL  INFORMATION 


Meetings  are  open  to  the  public;  however,  attendees  are  encouraged  to 
join  the  Boston  Computer  Society  (BCS).  This  newsletter  is  free  to  members. 
Backissues  are  one  dollar  each. 


FOR  MORE  INFORMATION 

Sue  Mahoney,  Director  of  the  Sinclair-Timex  User  Group 
c/o  The  Boston  Computer  Society  or  call  (203)  573-5816. 

Cliff  Danielson,  Newsletter  Editor 

14  Davis  Road,  Chelmsford,  MA  01824,  (617)  256-4638. 

John  Kemeny,  Contributing  Editor  &  Correspondent  With  Other  User  Groups 
284  Great  Road,  Apt.  D5 ,  Acton,  MA  01720. 

Library  Committee:  Beth  Elloitt,  Sean  O'Rahilly,  and  Bob  Sanchez. 


DIRECTIONS  TO  THE  MEETING 

The  Sinclair-Timex  User  Group  meets  in  the  Large  Science  Auditorium  (Room 
8/2/009)  of  the  University  of  Massachussets  of  Boston,  Harbor  Campus.  The 
Harbor  Campus  is  only  3  miles  from  downtown  Boston  and  easily  accessible  by 
public  and  private  transportation.  From  the  north  or  west,  take  the  Southeast 
Expressway  to  Exit  17.  Turn  left  onto  Columbia  Road.  Enter  the  rotary  and 
take  the  first  right  (Morrissey  Boulevard).  Bear  right  on  the  traffic  island, 
following  UMass/Boston  sign.  Turn  left  into  the  Campus.  From  the  south,  take 
Morrissey  Boulevard  northward  to  the  campus.  On  the  MBTA,  take  the  Red  Line 
(Ashmont  Train)  to  Columbia  Station.  Transfer  to  the  free  University 
shuttlebus  in  the  T  parking  lot. 

IMPORTANT  NOTICE  !  If  the  mailing  label  on  this  newsletter  is  handwritten 
(except  if  your  a  user  group),  then  you  are  not  on  the  mailing  list  of  the 
Sinclair-Timex  User  Group.  You  need  to  either  join  the  BCS  or,  if  you  are  a 
BCS  member,  contact  Mary  McCann  in  the  BCS  office  to  be  added  to  the 
Sinclair-Timex  mailing  list. 


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