The DLMS-2 provides the user with the ability to determine the true status of the operating port. When the Data Line Monitor is inserted between the data terminal and the data transmission equipment, it continuously monitors and displays the seven most critical lines of the RS232 data path. The indicators show red for a positive high and green for a negative low. The monitored lines are: Transmit Data (TD) pin 2, Receive Data (RD) pin 3, Request to Send (RTS) pin 4, Clear to Send (CTS) pin 5, Data Set Ready (DSR) pin 6, Data Carrier Detect (DCD) pin 8, and Data Terminal Ready (DTR) pin 20. Each LED circuit draws about 3 ma and operates in the EIA range of 3.5 to 25 volts. The chrome plated metal enclosure provides shielding and can take extensive abuse.