be provided by a pull-up resistor or gate as described before (see Figure A-1). Many modems expect a DTR high signal and issue a DSR. These signals are used by software to help prompt the operator about possible causes of trouble. The DTR signal is used sometimes to disconnect the phone circuit in preparation for another automatic call. It is necessary to provide these signals in order to talk to all possible modems (see Figure A-1). Figure A-1 is a good minimum configuration that almost always works. If the CTS and DCD signals are not received from the modem, the jumpers can be moved to artificially provide the needed signal. Figure A-2 shows a way that an EIA-232-D connector can be wired to enable a computer to connect to a basic terminal with only three wires. This is because most terminals have a DTR signal that is ON and can be used to pull-up the CTS, DCD and DSR signals. Two of these connectors wired back-to-back can be used. It must be realized that all the handshaking has been bypassed and possible diagnostic messages do not occur. Also, the TX and RX lines may have to be crossed since TX from a terminal is outgoing but the TX line on a modem is an incoming signal.
