Hop Box : A telephone relay proposal

Well it's 5:30 in the morning and I can't get to sleep, so I though that
I would write a quick article. Due to the time constraints this article
will be short and in more or less rough draft form. If there is a demand
for it, I'll write up a more detailed article at a later date.

Introduction

What is
a hop box? A hop box is a telephone relay device that connects two or
more phone lines together. Reasons for using one are varied, from not
paying toll charges to making tracing extremly annoying. This box is only
theoretical. I have not built one, though the design should work.

Overview

The simplest
configuration are two phone lines connected to a single box. The box has
an IN line and an OUT line. When call the IN line,
the device should pick on the line before the phone rings. It will then
directly connect you to the OUT line.

Software
Design

You should
confine the time of operation to specific off hours. For example, 2am
through 3am for dial in time. I would also recommend use of a password
via DTMF that is based on a rolling code algorithium. Whether it is a
revolving list of near one-time passwords or time dependent shouldn't
matter. The OUT line should also be configurable on-line. Meaning
that there should be a mechanism to program it via DTMF. Such things as
changing the access time, going 'silent' until a particular date or confining
the OUT line to certain numbers are all ideas.

Hardware
Design

The device
should be very small, near or completly waterproof, simple but flexible
jack connection(s), low power or no power requirements, no line voltage
drop when in 'silent' mode and cheap to manufacture. Let's cover each
top individually.

The size
of the box should be as small as possible for consealment purposes as
well as manufacturing and transportation. Depending on the need for a
battery, 3" x 2" x 1/2" should not be unresonable. By using today's microcontrollers
and ICs designed for telco applications, the total number of ICs should
be around 5.

Due to the unknown location of the device, from being placed in the ceiling to
being left outside, the box itself should have a variety of ways to secure
it physicaly. The following is a list of ideas: double-sided sticky tape,
wire ties, screws, string and gravity. Shock resistance is an idea, though
may not be worth the expense pending on the proposed environment.

Jack connections
should be the simple RJ type as well as screw jacks. Bannana or similiar
jacks are an option. The more flexiblity that you put into the box, the
more useful the box will be in the field.

Power requirements
will depend on the sophistication of the designer as well as the purpose
of the device. If the device is not to be detected by monitoring the line
level, then a battery would be required. For less secure targets this
is not an issue.

While in
'silent' mode, the device should directly connect the IN line to
the OUT line. While in this mode it will not pick up the line,
however it will also be near undetectable depending on the design. There
should be a way to make the box 'live' again. I would recommend both using
a calendar chip as well as a physical button.

Conclusion

Well that's
the 30 minute tour, which is about how long it took me to write this.
Please note that I will NOT be releasing a full schematic of this
box, nor will I be selling it. If you want to build one of these, you
will have to do it for yourself. Otherwise I hope you enjoyed the read.
If you have any suggestions regarding the box, please feel free to email
me at: silerepraeses@hackinthebox.org

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