It gets better. On Wed, Jul 27, 2011 at 12:01 PM, Don Kuhlman <[email protected]> wrote:
> Wow - my head hurts > > *From:* Ben Scott <[email protected]> > *To:* NT System Admin Issues <[email protected]> > *Sent:* Wednesday, July 27, 2011 10:41 AM > *Subject:* Re: Serial-to-USB Kit > > On Wed, Jul 27, 2011 at 10:21 AM, <[email protected]> wrote: > > ... I'm looking ... for a kit rather than an adapter .. > > Welcome to the world of RS-232. Buckle up. > > > ... needing a DB-9 female end, and what I've come across so far is all > DB-9 male ... > > RS-232 ports are either DCE (Data Communications Equipment) or DTE > (Data Terminal Equipment). > > Classically, DCE was the modem and DTE was the teletype/dumb > terminal. Since computers classically connected to a modem and > emulated a terminal, computers almost always provide DTE ports. > > The pinouts of DCE vs DTE connectors are different; the cables are > normally straight-through. If one wishes to connect DTE to DTE (or > DCE to DCE), one has to used a "null modem" cable/adapter, which > switches the pins. It's analogous to a "crossover cable" from > Ethernet. > > Console ports might be either DTE or DCE. (If they're DTE it's > easier to connect them to a modem for remote access; if they're DCE > it's easier to connect a local terminal. Some designs went one way, > some the other.) > > When it comes to D-subminiature connectors, almost always, DTE ports > are male, and DCE ports are female. > > Given the sexed nature of RS-232 connectors, a straight-through > cable or adapter will almost always be male on one side, and female on > the other. Null modem adapters/cables will almost always be the same > gender on both ends. > > One occasionally encounters transvestite ports: Female with DTE > pinout, or male with DCE pinout. > > There are 25-pin and 9-pin flavors of both DTE and DCE ports. In > almost all cases, we don't care about the extra pins on the 25-pin > connectors. So the two sizes are equivalent for our purposes. > > Given the above, one might normally expect 25-pin/9-pin adapters to > be straight-forward, but then things get complicated by adapters which > are also null modems or gender changers. > > > ... RJ-45 console ports ... > > Be aware that there's no real standard for RS-232 serial on an RJ-45 > 8-pin connector, so you may need more than one kind of > RJ-45/D-subminiature adapter. > > > Anyone know (part number or catalog number especially welcome) of a kit > with > > an assortment of modules so that one can plug one of its end pieces to > the > > end of a cable terminating in a USB at the other end? > > USB and RS-232 are totally different animals, so there is always > going to be an "intelligent" device involved. Since one typically > uses a USB/RS-232 adapter on a PC, such adapters almost always present > a male DTE port, same as the built-in ports of old. > > > ... I'm looking ... for a kit rather than an adapter .. > > Given the above, you're not going to find an easy one-size-fits-all > product. Typically one treats these as separate problems: > > (!) One has an USB/RS-232 adapter to get an RS-232 port on PCs with only > USB. > > (2) One maintains a fleet of RS-232 adapters. Typically: > > * DCE 25-pin/9-pin > * DTE 25-pin/9-pin > * 25-pin null modem > * 9-pin null modem > * 9-pin female/female gender changer > * 9-pin male/male gender changer > * 25-pin female/female gender changer > * 25-pin male/male gender changer > > Plus whatever RJ-45 variants you need. > > (3) Given the fleet of adapters, you just need some 9-pin straight > cables. Alternatively, some places decide to use UTP RJ-45 straight > through everywhere (since they already have it for Ethernet), and put > RJ-45-to-D-sub adapters on everything. > > Are we sufficiently confused yet? > > -- Ben > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > --- > To manage subscriptions click here: > http://lyris.sunbelt-software.com/read/my_forums/ > or send an email to [email protected] > with the body: unsubscribe ntsysadmin > > > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ > ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ > > --- > To manage subscriptions click here: > http://lyris.sunbelt-software.com/read/my_forums/ > or send an email to [email protected] > with the body: unsubscribe ntsysadmin > ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to [email protected] with the body: unsubscribe ntsysadmin
