Allen Tel Products ATMT25-MF RS232 Male To Female Mini-Tester RS232 Mini-Tester Male to Female Provides method of diagnosing RS232 interface problems Connects from the RS232 port to data line or modem LEDs indicate the status of pin 2 (transmit data, TD), pin 3 (receive data, RD), pin 4 (request to send, RTS), pin 5 (clear to send, CTS), pin 6 (data set ready, DSR), pin 8 (carrier detect, CD) and pin 20 (data terminal ready, DTR)