Re: Cuseeme Cameras

Barry L. Lankford (barryl@hiwaay.net)
Wed, 26 Jul 95 23:26:57 CDT


Fred Salerno <salernof@gate.net> wrote:
>Tiger Direct sold a camera with an RCA composite output which mounted
>above your computer monitor, and i believe it also had a mic. It sold for
>$370 last time I heard.
>
>On Thu, 27 Jul 1995, Barton Dring wrote:
>
>> I have been having great success with Cuseeme PC ver 0.65b3.
>>
>> I am using..
>> WIN 95
>> 486-25 16-Meg
>> VideoLogic Captivator
>> Father's camcorder (he wants it back)
>>
>> I would like to get one of those cheapo "camera on a card" things being
>> offered by companies like Polaris Industries. Has anyone used one of
>> these?. What is the video out on these? They say 75 ohm RCA plug.
>> Isn't 75 ohm more like the threaded cable company connector? If it
>> is, do I need an adapter or do I have to have an intermediate device
>> like a VCR tuned to channel 3 or 4?
>> If anyone is using one of these cameras successfully, I would love to
>> hear what is required. Thanks

When the output of a TV camera is referred to as having a "75 ohm"
connector, they are really referring to the source impedance of the
composite video output, not the connector. TV cameras, as far as I know,
always have 75 ohm outputs and usually have either RCA or BNC jacks. A
device with 75 ohm source impedance should be hooked up with cable having
75 ohm characteristic impedance, such as RG-59, and the connectors should
be chosen to match those on the equipment at both ends.

The RCA connector is the familiar push-on "phono jack" commonly found on
audio equipment and is a non-precision connector which doesn't have a
specific characteristic impedance. It just has to physically fit the
cable used. The "threaded cable company connector" is usually called an
"F" connector and is also a non-precision connector without a specific
characteristic impedance, but they are usually used for RF connections on
TVs and VCRs, not for composite video. Consumer video equipment usually
uses the RCA phono jacks for composite video output, and professional video
equipment usually uses BNC connectors, which is a precision connector made
in both 75 ohm and 50 ohm varieties. The internal diameters of the BNC
connectors are carefully controlled to maintain the specific characteristic
impedance of the cable through the connector when mated with its opposite
gender. The BNC connector is one which uses a bayonet arrangement to
connect the plug to the jack with a half-twist movement.

The camera on a card that you mentioned apparently has the usual 75 ohm
impedance and uses the RCA phono jack as its connector. This is probably
the same kind of connector that is on your father's cancorder, and the
same cable should work. I am not familiar with that particular camera
however, so I can't comment on its' suitability for CUSM. Most B & W
"security" type cameras should work with CUSM, although most are highly
sensitive to near infrared, and tonal values will likely not be quite right
unless an IR blocking filter (expensive) is used. Most people don't find
the unfiltered picture objectionable however. The camera for $370 mentioned
above sounds way over priced for a B & W TV camera. I'd look around for
something closer to $150 to $225 or wait for the PC Connectix camera for
about $100.

Barry L. Lankford email: barryl@HiWAAY.net Amateur Radio: N4MSJ
Madison, Alabama, USA ICBM: 34deg 41min 52.2sec N, 86deg 45min 34.2sec W
I have a new e-mail address, but the old one (barryl@nuance.com) still works