[GreenKeys] DTE & DCE on a modem

[Michael O'Day]

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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