A SELECTIVE SWITCH FOR GETTING MORE COMFORTABLE SCANNING
written by Dr. Fraud
In thiz short article, I will show you an easy possibility to get a more com-
fortable way to make BB-calls and scannings. Most of you use one of the fol-
lowing ways to call:
1.) U pick up the handset of the phone; you get a dialtone. Then, you dial
the number you wish to call. If BOXING fails, you hang up and try it
2.) U send a "HIGH" to yout LPT port. This causes a little circuit to open
the line. You get a dial tone...and you dial....
Of course, both of these methods are pretty nice...but here`s a better way to
get control over your line status:
Its possible to control the line with a little switch that always "listens"
to your soundcard`s output; if that switch recieves a tone of a certain fre-
quency (and you can tell the circuit what frequency this should be), it pro-
duces a "HIGH". This can be used to open/close a relais.
NOTE: There's a blueprint picturefile with this article, called BB-PLAN.GIF !
Question: Why do I need that circuit ?
Answer : Simple. Cause it`s comfortable and easy to use. Okay... before I
tell you more of that question/answer rubbish, you should take a
look on that phunny plan in that tiny GIF-picture. (BB-PLAN.GIF)
First, here are the materials you need to build up the switch:
C1= 2,2 uF
C2= 47 nF
C3= 100 nF
C4= 10 nF
P = 20 K
D = common diod, as e.g. 1N 914
IC= 567 (LM 567, NE 567 etc.) ...costs `bout 1$/piece...
You can build this thing any way you want... there are no critical values
you must pay attention for. Here are some electrical data:
- supply range: 4,75V to 9V
- supply current typ: 7 mA
- Input resistance: 20K
- smallest detectable input: 20mV (!)
- highest centre frequency: 500 KHz (!)
As you can see, the electrical data allow an universal use of that switch.
The resonance-frequency is defined as follows: Fo=1/(P*C4)
The band-width is the following: B= sqr(Ue/Fo*C4) ! NOTE: Depends on Ue !
It`s adjustable from 1% up to more than 10%. This means, that, if you adjust
it to 1%, a 1000 Hz tone will only be recognized from 990 Hz up to 1010 Hz.
If you use 10%, you will be able to send 900 Hz up to 1100 Hz to get a
response from the switch.
Question: How Do I use that phunny switch ?
Answer : Simple. Just connect it via a relais (ca. 5V) to your phone line.
The output voltage (pin 4+8) should be used to control the "prima-
Question: And then ?
Answer : Then you only have to move the trimmer until the relays "clicks"
when you send the frequency you want. Some dialers (e.g., the
latest SCAVENGER dialer) support that. If you wanna get off-hook
and on-hook again in an easy way, just connect that device to your
soundcard/phone line (Ue) and you will have a great utility to get
a phree line within about 2 seconds just by pressing a stupid little
key. The relais will stay open as long as that tone is recieved.
Note for practical use: If you decide to use that system, you should pay at-
tention to the following advices:
1.) The value of P depends on the frequency you wanna use. It`s useful to use
(haha...nice english) a frequency that is above the "normal" signalling
frequency (e.g. 3900 Hz.)
2.) Depending on that value, the value of the poti can vary... just look for
a good frequency, get the correct value and use the correct resistor for
the poti. Sometimes, it`s more than 20K.
3.) Avoid interferences. If you don`t, (e.g. you send a 3000/3001 Hz signal),
the behavior of the switch will get unstable. In fact, this can be also
quite useful (Analyst, u know...), but normally, it`s senseless.
4.) Block your output. Sometimes, you connect your soundcard`s output with
any devices without checking whether they are potential-free. This means,
that if you connect your soundcard to the phone-line _and_ to that switch,
you may get a problem `cause your signal is not potential-free. Avoid that
while using a simple transformator. It costs about 2$ and really prevents
your computer from getting unexpected noise/voltage/damage.
Okay... if you still don`t know the use of my tiny switch, then you are:
4.) stupid & lame
Hmm...check it out... if you`ve got any problems, just contact me at L.O.R.E.
BBS at any time !