RS232 monitors are quite common but most of them use the standard good old DB25 connectors. The majority of the RS232 ports in use today however use the smaller DB9 connector. This forces the use chains of adapters to get the commercial monitor/breakout boards working. The GGLABS T232 solves the problem by providing native DB9 connections.
The circuit is trivial. Every line is connected to a LED through a 1Kohm resistor. One 9-pin resistor array is used to reduce the overall size. Multiple locations for the LEDs are provided to support standard 3mm round, rectangular and DIL LED arrays. Both regular LEDs and bi-color LEDs can be used.
DIP switch SW1 can be used to disconnect any of the signals that can be manually rewired using jumpers connected to J3 and J4.