Up for sale is a rare piece of computing history: a **Protocol Computers, Inc. Model 71B/SNA Protocol Converter**. 

Dating back to the 1980s enterprise computing boom, these units acted as a critical bridge in IBM mainframe environments. The 71B/SNA translated data streams between IBM's proprietary Systems Network Architecture (SNA) protocols and standard Bisynchronous (BiSync) or SNA/SDLC configurations, allowing standard local terminals and printers to talk to massive host mainframes.

Notably, PCI was an OEM developer during this era that famously designed similar cluster controllers to bridge early Apple Macintosh and Lisa computers into IBM networks.

### Internal Hardware Features

The internal motherboard is an absolute paradise for vintage tech collectors and repair enthusiasts:

* **Processors:** Powered by classic **Zilog Z80A CPU** and peripheral support chips (CTC, etc.).

* **Configuration:** Includes four banks of classic CTS 206-8 blue DIP switches for configuration.

* **Firmware:** Populated with vintage socketed ROMs containing firmware revision 71B4.03.

* **Build Quality:** High-quality modular construction typical of 1980s enterprise-grade hardware.

### Cosmetic & Physical Condition

* **Front Panel:** Clean acrylic front faceplate with legible lettering. Internal LED indicators (PWR, SYS TST, SNA/SDLC, and 3-Port Bi Sync status) are intact.

* **Chassis:** Sturdy metal enclosure showing typical minor scuffs and shelf wear consistent with age. 

* **Internal Board:** Excellent visual condition. No signs of leaking capacitors, burned traces, or loose components. 

### What's Included

* PCI 71B/SNA Protocol Converter Unit only. 

*(No manuals, original boxes, or interface cables included).*