Review on 🔌 Cablemax RS-232 LED Link Tester - DB-9 Male to DB-9 Female Connector by Eric Young

This device is perfect. The LEDs are bi-color LEDs, glowing green when the voltage is high (unconfirmed) and red when the voltage is low (confirmed) so you can tell TX from RX without having to transmit data - it's very simple , to recognize the most common problem . ie whether it is DTE or DCE (and whether you need a null modem or not). You can immediately see if modem control is active, even if it is not active. The only thing that can improve this is a jumper. Holes and jumpers to quickly fix two mismatched connectors. But that would make it a junction box and not just a tester.