Trunk Mounted Split
Systems
In Cab Systems
Camcorder Systems
The in cab camcorder systems
were some of the first to be introduced. This system usually mounts the camcorder
on the dash of the vehicle. The major advantage of a camcorder system is easy
installation and easy removal for scene recording. This advantage also is a
disadvantage since some officers who take the vehicles home remove the camcorder
and use it for personal use. This relatively large object mounted on the dash
can become a projectile in an accident. For insurance reasons some PDs can not
install camcorders on the dash of the vehicle. Camcorders are also designed
for non-continuous usage and usually carry a short warranty period. Camcorders
can be significantly more expensive to repair than standard VCRs which presents
a problem if regular maintainence is not performed on the camcorder. Since camcorders
are mounted on the dash they recieve the full extent of summer sun. This heat
can actually melt the plastic enclosures and cause irreparable damage.
In the beginning full
size VHS camcorders were used that could record a full 8 hrs with a T160 video
tape in the EP mode. Currently there are no full size VHS camcorders on the
market that can record in the EP mode, limiting the recording time to 3 hrs
with a T-160 tape. When using a VHS-C camcorder the record time is even shorter.
The most you can record with VHS-C is 1 hr with the longest tape. 8mm camcorders
have a time restriction of 4 hrs. This reduced recording time without changing
tapes is the major limitation to dash mount camcorders.
The video camera in
camcorders is usually of good quality and has at least a 12X zoom with auto
focus and auto iris functions. This means you just point the camcorder and
a good picture is recorded. Typically the camera portion of a camcorder has
specifications equal to the best split system on the market today. A user
must compare Lux rating @ the f-stop (e.g. F1.4), zoom range (digital or optical)
and resolution. These facts are not easy to find in camcorder specifications
but are very popular advertising specifications in split systems. The quality
of a video picture is also very subjective to an individual and a particular
usage. It is recommended the user not purchase video systems based on specifications
but true in-car comparison.
For example, a police
department purchased a low light B&W camera system with 0.2 Lux @ f1.4 rating
using a f1.8 Vari Focus Auto Iris lense. They did not like the way the camera
worked at night when they would go by bright lights or when getting a license
plate number using their headlights. The reason was the camera was too sensitive
and the zoom lens could not zoom in all the way to the license plate so the
auto iris function could work properly. The PD traded the camera for a color
one that was rated at 2 Lux @ f1.4 using the same f1.8 lens. The camera performed
much better and was acceptable by the PD. The reason was the new camera was
10 times less sensitive at night and this was the application for which this
PD was purchasing the video system. Of course there are several other ways
to solve this customer’s problem, but the point of this example is that specifications
can be misleading when the end result is subjective.
Normally camcorders
have to be manually initiated to go to the record mode. This can be cumbersome
and is sometimes forgotten in critical situations. Some vendors can activate
the camcorders to record automatically via take down lights or some easily
accessible switch.
Camcorders also can
be fitted with remote wireless microphones. Wireless microphones will be discussed
later since there are many makes and models with various quality levels. Nonetheless,
camcorder systems should be fitted with wireless microphones for a full video
and audio record of the events.
Most camcorder systems
on the market today have the Time and Date inserted into the video via the
camcorder. This is settable on the camcorder via pushbuttons. Since this feature
can be turned on it also can be turned off. This leaves a potential problem
if the T/D is disabled and an event occurs for legal reasons. Make sure this
feature can be permanently set or at least difficult to disable.
Camcorder systems do
not contain any type of heating or cooling. In extreme enviroments the camcorder
is removed and stored in normal room temperature and put in a vehicle after
the cab is up to normal temperatures. If the camcorder is not removed and
is allowed to stay in an extremely hot or cold vehicle, the camcorder must
be heated or cooled to operational temperature before any video can be recorded.
Camcorder systems are
not covered by any patents. This means the cost does not include the royalty
payments to patent owners, which gives this system the lowest cost of any
in- car police video system.
In Cab Split Systems
In cab split systems usually
include a dash mounted camera connected to a VCR, which is mounted under the
seat, behind the seat, on the passenger side floor, or under the dash. There
can be a remote control unit to operate the VCR as optional or included equipment.
The major advantage of this type of system is that it does not require patent
licensing and still has all the advantages of a standard VCR. This type of system
operates just like a trunk mount system but without the VCR in the trunk. Since
the VCR normally stays in the vehicle, it is supplied with or without heating
and cooling. For areas that have extreme cold, it is recommended a heater be
included in the unit to bring the VCR to operational temperature. In extreme
heat a fan is usually supplied to use the cool air in the cab to blow through
the enclosure for bringing the VCR into operational temperature.
Trunk Mounted Video Systems
Trunk mounted systems are
very similar to in cab split systems. The major difference is that when mounting
a VCR in the trunk it needs to be temperature controlled, either heated or cooled.
For most parts of the U.S., heating via resistive heating elements in the winter
is used in conjuction with a fan. The fan alone in the summer is usually enough
to maintain operating temperatures of the VCR. Some trunk installations use
the air from the cab via a duct to eliminate the need for expensive heating
and cooling devices. In extreme heat, other systems using heat pumps have been
used. This requires a sealed VCR case and thermonic or compressor devices which
are extremely inefficient and consume large current draws from the battery and
alternator.
Some type of shock mounting
is required to reduce sharp vibrations which can dislodge internal components
and cause the tape to jump out of the tape path causing tape jams. Some vendors
put padding inside the vault and some use shock mounts on the outside.
Up front in the vehicle
is usually a control head to give user feedback and controls for the VCR operation.
These control heads either mount overhead or on the equipment console. The
reason for overhead is to free up space on the equipment consoles in the ever
crowded modern police vehicle. There are also handheld controls that lay next
to the seat on an embilical type arrangement. These handhelds are usually
the most cost effective, with the monitor separate from the control head.
Overhead consoles either have internal or external monitors. The newest technology
has a recessed LCD monitor for a very low overhead profile. In most sytems
that use LCD monitors, care has to be taken in mounting so direct sunlight
does not shine on the monitor which makes it very difficult to view.
The camera of a trunk
mount system is usually mounted on the dash board, from the windshield or
from the ceiling. Any kind of camera configuration can be used but most high
end systems use an automatic color camera with electric zoom and auto/manual
focus.
Many features available
on these high end products vary from vendor to vendor. Some of the most useful
features are listed below:
- Record Protection
This feature insures that videotape can not be rewound and recorded over
any portion of the tape. This can be done in software by not allowing the
user physical command over the VCR to do this. Other vendors record a unique
number on the tape in each video picture or continuously on the audio channel.
An interruption in the continuity of this recording will be visible or audible.
- Take Down Light
Activation
This is where the VCR is automatically triggered to start recording when
the lights, siren or pursuit mode lights are turned on by the officer. Usually
the VCR records for a short period after the lights are turned off to view
the target vehicle leaving the scene.
- Time Remaining
on Tape
This feature gives the user a running time of how much recording time is
left. This allows the officer to replace a tape when nearing the end so
no event is lost.
- Function Inputs
These are inputs that when connected to lights, siren, etc put on-screen
text that is recorded on the video for verification the vehicle had these
functions active. This is important for legal proof of correct procedure
execution.
- Auxillary Data
Ports
This is additional data input ports for on-screen radar gun data, computer
interface or BAC data from Breathalizers.
- Wireless Trigger
With this function, when the wireless microphone is turned on the VCR automatically
starts recording. This can be via tone code squelch or RF carrier detect
circuitry.
- Low Tape Warning
This is an automatic feature that is constantly monitoring the tape left
and can initiate an audible alarm when the tape is very close to the end.
Many other features
are available and the PD should determine which ones are of importance
to their particular operations.
Trunk mounted police
car video systems are covered by patents and the selling agent must be
licensed or face legal action.
VCRs
In car police video systems
have all types of VCRs, usually of standard VHS type. The standard full size
VHS is most desireable due to the long recording times of up to 8 hrs with a
T-160 tape using the VCR in the EP mode. There are T-180 tapes that can also
extend the recording time to 9 hrs.
Some manufacturers use
2 head VCRs and some use 4 head VCRs. All VCRs, whether 2 head or 4 head,
use 2 heads to record the tape regardless of the recording speed. A 4 head
VCR only uses the 4 heads during playback pause mode or special effects. A
4 head VCR only uses 2 heads to playback a normally recorded tape. This means
that a tape recorded on a 2 head VCR will look just as good when played back
on a 4 head VCR as a tape recorded on a 4 head VCR. For in car video systems
the use of 4 head VCRs are only for playback quality within the car itself.
The importance of a 4 head VCR is almost none except to give the user a false
sense of quality difference between a 2 head VCR and 4 head VCR. The important
feature of a VCR is the recording quality and not the playback since the tape
is removed from the vehicle and reviewed if a problem has been identified
anyway.
Most standard VHS VCRs
are specificed to have a recording resolution of 240 lines. Some industrial
models can give up to 350 lines of resolution. SVHS VCRs can give over 400
lines of resolution. Resolution is the measure of the amount of detail or
clarity the playback picture contains. All VCR manufacturers specifiy resolution
in SP mode. Almost all video systems are operated in the EP mode which gives
the longest recording time. In this recording mode the manufacturer usually
does not specify resolution since it is so low. You can see the difference
yourself when you record for a short period in each mode and compare. Typically
a VCR rated at 240 lines in SP will give about 180 lines in EP.
Another parameter that
is misunderstood is S/N (Signal to Noise Ratio). This is the crawling noise
in the video or the streaks in the video. Again VCR manufacturers specificy
this at the SP mode and a good number is 46 Db and above. When you record
in the EP mode this number can drop well below 40 Db. You also can not expect
the EP S/N Ratio to be better when the SP mode is better. Usually this is
the case, but some VCRs are peaked for SP and EP falls way below that of other
VCRs even if the SP was lower in the beginning. As stated before, since all
of this can be very confusing, believe your eyes, not the specification.
There does exist different
quality levels between various VCRs on the market today. There are consumer
type VCRs and industrial type VCRs used in various systems. There is a false
sense of superior quality of industrial over consumer VCRs. There are many
consumer VCRs that are higher quality than industrial VCRs. The only definition
of the difference between the two categories (as defined by the US Customs
and UL Laboratories) is the following:
Consumer VCRs have two
prong AC power cord and RCA video input/output jacks.
Industrial VCRs have
a three prong grounded AC power cord and BNC video input/output jacks.
These are the only differences.
In fact most VCR manufacturers use the same internal mechanism for their consumer
and industrial models. Some manufacturers actually use older models of mechanisms
for the industrial models since the sales quantity is so low they do not want
to spend the money for model redesign.
The different manufacturers
also have different quality in the deck mechanism itself. The deck mechanism
is the actual mechanical part of the VCR that loads the tape and plays and
records video on the tape. In the past 15 years the mechanisms have gone through
tremendous amount of change. Most mechanisms are made of punched and bent
metal. Some mechanism are made from die cast chassis. Several years ago the
diecast chassis gave better stability of the tape path which yielded a better
picture quality. At this early stage the servo control was very basic and
drive motors were primitive. In recent years the servo electronic control
and advanced motor design have eliminated the need for die cast chassis. Actually
the best mechanisms on the market today are made of bent and punched metal
with advanced servo control. The perceived durablity and superior quality
of die cast chassis over other types is simply not true.
The true evaluation of
a particular VCR is not the recording and playing back on that VCR. The correct
evaluation would be to make a tape on a vendor’s system and evaluate the playback
on another high quality VCR in the PD. Remember, the major advantage of a
4 head VCR in the vehicle is to review and pause recorded video while in the
police car, which yields a noiseless and flickerless picture. If this is a
requirement of your video system then a 4 head VCR is required.
VCR Mounting Configurations
- Horizontal
Most commerically available VCRs are designed to operate in the horizontal
position. The internal tape path is designed for this configuration. If
mounted out of this geometry there may be a chance for the tape to jump
out of the tape path and cause a jam.
- Vertical
Most camcorders are operated in the vertical position. The tape loading
of a camcorder is different from a conventional VCR, allowing for greater
head tension which allows operation in the vertical position. Many conventional
VCRs, although designed for horizontal, have been operated in the vertical
position with no ill effects. This is mainly VCR dependent.
Video Tapes
Care must be taken in using
video tapes of good quality. Low cost tapes have higher drag on the hubs which
can reduce the service life of the VCR. T-120 tapes are the most common. They
give 6 hrs of record time when the VCR is in the EP mode. The T-160 tapes give
8 hrs in the EP mode. T-180 tapes give 9 hrs of recording in the EP mode. The
difference between these tapes is the physical length of the tape on the cassette.
The more tape the longer the recording time since EP is the slowest recording
speed for VHS VCRs. The T-160 tapes usually have the same type of tape as the
T-120 but just more of it. The T-180 is actually a thinner tape so the manufacturers
can fit more on the same cassette.
Brand new tapes all
have a certain amount of ferrite dust on the tape. This is loose particulars
of the magnetic material on the tape that the manufacturer could not remove.
When you record a tape for the first time all this dust goes into the VCR.
This is a major contributor to head clogging and dirty VCRs. New tapes should
be recorded once on a test VCR before put into the field. If this procedure
is adhered to, the VCR will give a longer service life.
B&W Cameras
B&W cameras normally have
a lower (better) light sensitivity. This is great for night use where ambient
light is limited. B&W cameras are also lower cost than color. It is this lower
cost feature that makes B&W atractive for video systems.
Color Cameras
Color Cameras normally have
a higher (worse) lux rating or are less sensitive than B&W. Color cameras are
recommended because of the ease of identification of suspects and objects with
the added advantage of color. Color cameras have internal color processing that
makes the colors look clear and bright or dull and fuzzy. This color specification
is usually left out of the specifications in most color cameras. Again we envoke
the subjective rule. Look at the recorded playback to make your decision. Color
cameras consume more power than B&W models, which reduces the recording time
on batteries.
Lens
All cameras have a lens
included. Some cameras have an integrated lens and some have an add on lens.
There are C mount lenses and CS mount lenses and some vendors use board cameras
in a box that have various types of non standard mounts. There are fixed focus
lenses that have no adjustment. VariFocus lens have a type of zoom control but
require refocusing after this control is moved. Zoom lens require no refocusing
on the full range of zooming. The high end cameras with built in zoom and focus
are completely automatic, yielding good pictures with no intervention regardless
of the situation.
Lux, F Stop, and IRE
These are the technical
specifications that few people understand about cameras and lenses. All cameras
have a Lux rating, and an associated lens with an f stop rating. Lux is the
rating of the amount of light required to see an image. The lower the Lux the
better, which means the camera is more sensitive to light and can be used in
darker situations. The f-stop is like an aperature that restricts the amount
of light getting in through the lens opening. The lower the f-stop the better
or the more light that can get to the imager of the camera. The hidden specification
is the IRE associated with the above specifications. IRE represents the level
of the video signal; 100 IRE is maximum white and 0 IRE is black. All the levels
of video fall in between 0 and 100 IRE. When a camera vendor says 2 Lux @ f
1.4 at 50IRE that means the following; When a camera is pointed at an object
illuminated by a light source of 2 Lux and the lens on the camera has a specification
of f 1.4 the video level coming out of the camera is half way between white
and black or gray. If a vendor rated the same specification but at 25 IRE that
camera would have 1/2 the sensitivity of the one rated at 50 IRE. There also
is an internal gain of the camera that is sometimes increased to give the required
specification but the picture is very noisy with the picture looking like it
is in a snow storm. If the above specification was 2 Lux @ f 1.2 at 50 IRE this
camera would be twice as sensitive. Remember that at 2 lux there is very little
color content. Most color cameras at low light conditions show no color at all.
The whole exercise here is to show you that a camera vendor can make a camera
look as good as they want with specifications. Again the only proof of qualtity
is the subjective test since there is no way to equally compare any two cameras
on the market today unless you are a qualified engineer with $20K worth of test
equipment.
Integrated Cameras
The integrated cameras create
a specification with the lens’ f stop built into the specification. To compare
this with a standard camera with an add on lens you have to understand how Lux
and f stop work.
Resolution Standard
VHS
Resolution is the measure
of highest frequency the camera can recognize. This is determined by the number
of pixels (eg 768h x 512v) the imager has which directly converts to resolution.
Some people consider resolution as the clarity of the picture which is again
a subjective opinion. Most color cameras used today have resolution starting
at 300 lines and up. The camera resolution as a rule should be greater than
the resolution of the VCR. Most standard VHS VCRs on the market today have color
resolution at approx. 240 lines. Higher qulaity VCRs can go up to 300 lines
but this is normally the maximum. If a VCR can only record up to 300 lines of
resolution the color camera resolution at 330 lines is already greater than
the VCR. This means the most you are going to get out of the VCR is 300 lines,
so why buy a 400 line color camera? The subjective opinion is again envoked
in this comparison. Do not buy a high resolution camera because it looks good
on a monitor, make sure the playback looks good on the monitor.
Resolution SVHS
SVHS is a newer format that
can give greater than 400 lines of color resolution. This format also requires
a SVHS camera and both must connect together using the SVHS connector system.
To view the new SVHS resolution you must also use an SVHS monitor. If one or
the other is not SVHS the resolution is reduced back to the 240 lines of a standard
VHS VCR.
Wireless Microphones
Lapel mounted wireless microphones
are almost a requirement in mobile police video systems. The need to record
everything an officer says is important in every legal action, and to hear responses
from the interviewee is also very important. The only way to guarantee both
recordings is to have the microphone mounted on the officer. Various types of
wireless microphones are available in various qualities and operating frequencies.
The lowest cost units utilize the 47 Mhz band. This frequency is shared with
remote telephones, radio controlled cars, garage doors and many other devices.
The sheer number of these devices on the market guarantee interference with
the audio in any populated area. Other units use 160 Mhz to 190 Mhz. These units
operate better since they generally were designed for high quality audio for
singers and musicians. Also this frequency range is less polluted with consumer
products. Newer units operate on the 900 Mhz spread spectrum frequency. The
technology in the frequency band eliminates overlapping by the spread spectrum
technology. This band can also be digital which will be the trend for the future
to completely eliminate noise and interference.
The biggest disadvantage
is that most of this wireless transmitters use a standard alkaline 9V battery.
You can expect 6-10hrs of operation and then you need to replace the battery.
If a rechargeable system is available this would eliminate many of the current
problems in the field of battery replacement.
Some manufacturers supply
units with tone code squelch that can be detected by the receiver to trigger
the VCR into record when the officer turns on the wireless microphone. Another
method is the receiver detects an RF carrier from the transmitter and turns
on the VCR. The squelch system is much more reliable since the receiver is
looking for a particular code from the transmitter while the RF carrier detect
senses only the presence of the transmitting frequency. If another device
goes by with the same frequency the RF carrier detect will turn on the VCR.
This is very rare but possible.
Trunk mounted antennas
must be installed and connected to the receiver in the vault in the trunk
or cab. If this antenna is broken or disconnected no audio will be received
or recorded.
Wireless Audio and Video
The new trend is to not
only have a wireless microphone on the officer but also a wireless camera. This
eliminates or adds to the internal camera on the dash. Usually these systems
must be FCC licensed so the user can possess a high power transmitter, so clean
video is always recorded. The systems that operate at 900 Mhz usually do not
have enough power to give quality video. The frequency of choice is 2.4 Ghz
with diversity antennas on the reciever to guarantee good video. These units
consume a significant amount of power from the battery pack on the belt and
must be recharged regularly. A lapel mount of camera and microphone are usually
2"x2"x1" with a wire to the belt pack which houses the transmitter and battery
pack.
Radar Gun Interfacing
Many video systems have
options for direct input to radar guns. Most new guns have an RS-232 port that
can connect easily to most video systems. Care must be taken in expecting older
style units to connect. Some models are unable to connect or require additional
converter boxes that increase the system cost. Also different manufacturers
of radar guns give out different information. Some give only target speed, some
only lock speed, some both, some patrol speed and target speed and not lock
speed. Check with the video system vendor and evaluate your radar gun stocks
to see if compatibility is even possible. Some radar gun manufacturers actually
void their warranty when connecting to video interfacing equipment. Assume nothing
here, get a working demo.
BAC Interfacing
There exists some vendors
who directly support connection of BAC equipment to the video system for verification.
AVE manufactures an add-on product called the VSI that overlays most manufacturer’s
BAC equipment data onto any video system for recording. Interfacing to video
gives a proof positive record of test results. This can also be used back at
the PD in the testing room.
Installation
Most PDs have their local
radio shop do the installation. This is perferrable to the shops that install
the consoles and light bars. This is only because technicians installing radios
are more familiar with electronic product installation and grounding. Improper
grounding on installation can cause interference in the video or radio or both.
Of course improper cable installation can cause broken connectors or heat damage
if near the muffler or catalytic converter. Most problems with mobile police
video systems are installation and the subsequent troubleshooting.
RFI and EMI
Sometimes the video system
will have interference from the radio when the microphone is keyed. This is
usually due to improper grounding on the radio and/or the video system. Some
PDs have high powered radios for use in large counties. If this is the case
the RF energy may be going directly into the camera, in which case a metal enclosure
must be installed around the camera. RFI and EMI must be approached on a case
by case basis and each vehicle will be different. Generally quality video systems
do not have this problem but eventually you might.
In Conclusion
Congratulations, you made
it through. We believe you now have the working knowledge to specify a video
system for your PD based on your needs and wants. The most important fact to
remember is to evaluate a video system to your specifications, not someone else’s.
