Take the tour ×  I have a modem connected to a server through
RS232. The server is constantly sending data to the modem,
whether the modem is connected or not.  When I try to connect to
the modem with another modem the handshaking fails because the
server is sending data that gets in the way.  I am looking for a
way of stopping the communication between the server and the
modem until the modem's DCD line is asserted.  What kind of
device or component could be used to design a small passive (no
power supply) circuit that could perform this operation?  As far
as I can tell it is only the TX line that needs to be
interrupted while the modem is off-line.  share|improve this
question @Handshaking I'm not sure this can be solved with
hardware alone. I'm assuming your modem can auto answer and
enters data mode once a connection is established. Why isn't the
software on the server waiting for the modem to be ready before
sending data? Also, are you certain the modem can't be
configured to ignore this data itself (ie,