Wiegand

The legacy one-way reader-to-controller protocol that dominated PACS deployments from the 1980s through the 2010s. Wiegand is unsupervised, plaintext, and uses a simple two-wire (Data0 / Data1) signaling scheme — making it easy to install but trivially vulnerable to wire-tapping attacks. The most common variant is 26-bit Standard Wiegand (8-bit facility code + 16-bit card number + parity bits); higher-security variants use 35-bit, 37-bit, or Corporate 1000 (48-bit) formats.

Wiegand readers don't support encryption, mutual authentication, tamper reporting, or remote firmware updates. They also have no return path — the reader can't acknowledge whether the panel received the bits. The protocol is being actively deprecated in favor of osdp in security-conscious sectors (federal, financial services, healthcare).

AE Guardian sees Wiegand only indirectly — via PACS connector reader / card-format metadata. Card numbers provisioned by AE must respect the reader's Wiegand bit-width; provisioning a 35-bit card number to a 26-bit reader will fail at the panel.