The image on the right shows a typical CPM-700 from the early 1990s,
with the special RF probe attached to it. The probe has a built-in
a pre-amplifier and a telescopic antenna, and can be waved
around the room like a magic wand.
The device has two modes for detection: search and monitor.
In search mode the receiver scans the entire frequency spectrum for
RF bugs, using one of the RF/LF probes connected to the PROBE socket at
the top right of the front panel. Please note that only original REI
(active) probes can be used, as they contain some internal circuitry.
Once a room is sweeped, the unit can be set to monitor-mode and
the treshold is adjusted so that the alarm is just silent. Whenever someone
brings a new eavesdropping device into the area, or when a remote controlled
or timed device becomes active, this will trip the acoustic alarm.
Any eavesdropping device found, will be hear through the built-in speaker
or, better, via the connected headphones. Apart from using one of the
probes to pick up RF signals, the CPM-700 can also be used to check any
type of cable for acoustic (audio) or carrier bugs using the AUX input
on the right side. This can be used, for example, to check analogue
telephone lines (PSTN).
The CPM-700 is powered by a removable battery pack that contains 8
penlight batteries of 1.5V each (12V) or 8 rechargeable NiCd batteries of
1.2V each (9.6V). It can also be power from the mains using the supplied
mains adapter, or any other suitable external power supply unit.
When using NiCd batteries, a slide switch in the battery compartment
has to be set accordingly. This allows the batteries to be charged
automatically when the external PSU is connected.
The unit comes complete with a
laptop-style carrying bag in which
all accessories are nicely stored.
All controls and adjustments of the CPM-700 are at the front panel. The
unit can be switch ON and OFF with the power switch at the bottom left.
At the top left is the socket for the headphones and the volume adjustment.
When headphones are used, the internal speaker will be disabled.
The next section (MONITOR) controls the built-in alarm that has both
an optical (red lamp) and an acoustic feedback (buzzer).
The buzzer can be disabled with the SILENT/TONE switch.
Most of the right half of the front panel is taken by the clear LCD screen.
The top half of the display contains the field strength indicator. The bottom
half contains five indicators that reflect the current state of the device.
At the far right is a BNC socket for connection of the probes. The unit comes
with an RF probe (the magic wand)
and an LF probe in the form of a power
adapter. The latter is used to search for acoustic (audio)
and for carrier bugs on the mains power lines.
Despite the fact that the CPM-700 was developed in the late 1980s, it is
extremely well built. The unit comes in a sturdy metal case with a metal
front panel. A separate battery compartment is accessible via a metal panel
at the rear by loosening two bolts. The CPM-700 has a surprisingly modern
look and feel, which is probably why the design hasn't changed in all these
can be accessed by removing four cross-head bolts from the sides.
A large double sided PCB is mounted at the bottom. It contains most of the
analogue and digital circuits of the CPM-700. A separate PCB hold the controls
and adjustments of the front panel. It is mounted vertically at the front of
the main board.
A rather large (and clear) loudspeaker is bolted to four mounting posts,
in such a way that it lines up with the grid in the top cover. In order
to prevent damage from leaking batteries, a separate compartment is present
at the rear.
The unit is very robust and most of the companents are easily accessible,
making the CPM-700 a service friendly device. The only weak spot (if there
has to be one) is the headphones socket at the top left of the front panel.
If it is broken (as it was in our case), you will have a hard time replacing
it, as the adjustments to its right are fixated with super glue, making it
virtually impossible to removed the front panel. In our case, we fixed it
by (carefully) cutting the existing socket to pieces first, then removing
the pieces and finally replacing it with a proper alternative.
Range15kHz-1MHz (LF probe), 50 kHz - >2GHz (RF probe)
Gain20 dB nominal (RF probe)
Sensitivity-38dBm (LF), -62dBm (RF)
Dimensions23 x 15.5 x 4.5 cm (main unit)
- Research Electronics Inc., Unit Operating Instructions, Model CMP-700
Original User Guide. Date unknown, but probably 1988.
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© Crypto Museum. Created: Monday 20 May 2013. Last changed: Wednesday, 02 December 2015 - 21:39 CET.