Black Box Corporation ME721A-F Asyc Short Haul Modem

Black Box ME721A-F Short-Haul Modem is a nonpowered, asynchronous short-haul modem (SHM-NPR) with a DB25 female connector, intended to link asynchronous devices to a host over short distances. The 4-wire, asynchronous design is used on a single twisted-pair or CATx link, and the unit is typically deployed in pairs (two SHM-NPRs) or with a companion Short-Haul Modem-B Async (ME800A-R3) to complete a full connection. When used over a single twisted pair, the Short-Haul Modem operates in half‑duplex, transmitting in only one direction at a time. The ME721A-F‑R3 variant is the commonly referenced revision for this family and is described as nonpowered, meaning no external supply is required. Its DB25 female port enables straightforward interfacing with host DTEs and remote devices while preserving standard signaling and pinout expectations, making it suitable for industrial automation, data acquisition, and other short-range serial extension tasks. In typical deployments, the ME721A-F-R3 is paired with SHM NPR to connect asynchronous devices to a host, or used alongside ME800A-R3 in mixed environments to bridge legacy equipment over short distances.