[GreenKeys] DTE & DCE on a modem

[Michael O'Day]

Hi Brooke,
Yes indeed they are, I was assuming his modem had a 25
pin connector. I guess I should have remembered what
happens when you do that.

9 pin  25 pin   Signal
 3       2       Tx
 2       3       Rx
 7       4       RTS
 8       5       CTS
 6       6       DSR
 1       8       DCD
 4       20      DTR
 5       7       Signal Ground
 9       22      RI

Also, on some data sets, pin 1 is connected to frame
ground, which might give you trouble if it causes an
AC ground loop. We used to pull all but the basic 8 
pins so the extra ones couldn't give us trouble later.

Mike - N9ODM
 
--- Brooke Clarke <brooke at pacific.net> wrote:

> Hi Michael & Larry:
> 
> Those pin numbers only apply to a 25pin connector. 
> They are different for a 9 
> pin connector.
> 
> Have Fun,
> 
> Brooke Clarke
> http://www.prc68.com/P/Prod.html  Products I make
> and sell
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> 
> Michael O'Day wrote:
> > Larry,
> > If you want to use the modem without a full RS-232
> > handshake, you may have to "hot wire" the modem by
> > connecting some of the signals together. We used
> to do
> > it by cutting the wires inside the cable's
> connector
> > shell, leaving a half-inch of wire on each pin to
> be
> > connected, and soldering them together inside the
> > connector shell. The basic RS-232 handshake is:
> > 
> > PIN #    Signal   Signal
> >  2         Tx     Data Transmit - to modem
> >  3         Rx     Data Receive -  to terminal
> >  4         RTS    Request to send - to modem
> >  5         CTS    Clear to send - to terminal
> >  6         DSR    Data set ready - to modem
> >  8         DCD    Data Carrier Detect - to
> terminal
> >  20        DTR    Data terminal ready - to modem
> >  7         GRD    Signal Ground - common to all
> > 
> > The hot wire sequence is tie pins 4&5 together,
> and
> > separately tie pins 6,8&20 together. There is also
> a
> > ring indicator signal on pin 22 (for auto-answer
> > modems), tell the modem to ignore RI if it has
> that
> > option.
> > 
> > Mike O'Day  N9ODM
> > 
> > --- Larry Tighe <larryradio at worldnet.att.net>
> wrote:
> > 
> >> Howdy Folks,
> >>
> >> Got my hands on some Black Box CL050A modems. 
> >> Planning to try keying a HV 
> >> transistor with the RS-232 outputs.  They are
> >> designed to key a current loop 
> >> which they supply 18 volts to.
> >>
> >> Can anyone tell me what DCE and DTE means?  There
> >> are dip switches that'll 
> >> have to be set up....
> >>
> >> Thanks,
> >> Larry
> >> www.antiquetelephone.com 
> >>
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> >>
> > 
> > 
> > 
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