SerialGear CM-41042 4-Port DB-9 RS232 to USB Adapter with Isolation and Surge Protection

Four-Port Industrial Serial Adapter

The SerialGear CM-41042 adds four DB9 male RS232 ports to a PC, thin client or server through a single USB connection. It targets engineers and integrators who need reliable COM-port expansion for legacy instruments, PLCs or point-of-sale hardware without opening the chassis. Each port handles 3-wire signals at rates from 75 bps to 921.6 Kbps and includes 512-byte FIFOs for smooth data flow.

USB 1.1 Bandwidth and Signal Constraints

The adapter operates natively on USB 1.0 and 1.1 and is forward compatible with USB 2.0 hosts, so total throughput across the four ports cannot exceed the 12 Mbps bus limit. Optical isolation rated at 2,500 Vrms and built-in surge protection guard connected equipment from ground loops and transients, but the device draws all power from the USB bus and supports only TXD, RXD and GND lines.

Replaces Single-Port Dongles and PCI Cards

This unit consolidates up to four individual USB-to-serial dongles or an internal multi-port card, freeing expansion slots and reducing cable clutter. The upgrade is worthwhile when an application requires simultaneous connections to multiple RS232 devices and the host has spare USB ports but no free PCIe or PCI slots. Buyers who need full modem-control signals or more than four ports should look elsewhere.