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- A SELECTIVE SWITCH FOR GETTING MORE COMFORTABLE SCANNING
- written by Dr. Fraud
- HI PHREAKS,
- 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
- again...
- 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-
- ry" side.
- 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:
- 1.) stupid
- 2.) lame
- 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 !
- Greetz,
- Dr. Fraud
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