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.