AT&T RLX-246 Packet Multiplexer 19" Rackmount V.35 RS-232 256 Kbps

AT&T RLX-246 Packet Multiplexer 19" Rackmount V.35 RS-232 256 Kbps

The AT&T RLX-246 is a 19-inch rackmount packet multiplexer designed to combine voice, data, and fax traffic over one or two dedicated or switched digital transmission facilities. It uses High-speed Time Division Multiplexing (HTDM) to aggregate multiple data streams up to a maximum of 256 Kbps, and supports simultaneous voice band processing across up to six channels. The unit was marketed under the AT&T Netrix product line and is a two-rack-unit form factor chassis with a full front-panel LED array for channel-level status monitoring.

Specifications & What's Included

• Model: AT&T RLX-246 Packet Multiplexer
• Form Factor: 19" Rackmount (2U)
• Power: 100/120/220/240V AC, 1.5A, 50/60 Hz (wired for 115V per rear label)
• US Patent: 4,782,485
• Transmission Facility: One or two facilities, dedicated and/or switched
• Dialing Options: EIA-initiated or V.25 bis for switched digital
• Bandwidth with HTDM data: 12.0 / 14.4 / 16.0 / 16.8 / 19.2 / 24.0 / 28.8 / 32.0 / 38.4 / 48.0 / 56.0 / 57.6 / 64.0 / 72.0 / 76.8 / 96.0 / 112.0 / 115.2 / 128.0 / 256 Kbps per facility
• Bandwidth without HTDM data: Adapts to any clock rate between 9.6 and 256 Kbps
• Maximum aggregate bandwidth: 256 Kbps
• Data Interfaces (Electrical): V.35, V.11/X.21, RS-422/V.36 (RS-449), RS-232/V.24
• Data Connectors (Physical): DB25 male with cable; DB25 female without cable
• Voice Band Channels: 2–6 channels
• Voice processing: VoicePacket (6.4–12 Kbps dynamic), or 4.8 Kbps CELP, or 7.4 Kbps CELP
• Facsimile: 9.6 / 7.2 Kbps on V.29; 2.4 / 4.8 Kbps on V.27ter; Group III fax machines only
• Voice/Fax Connectors: 8-position RJ-45 modular jack or 50-pin telco connector
• Front Panel: Voice Band LEDs (channels 1–6 IN/OUT energy/seizure), Data LEDs (channels 1–8), FAC 1–2 indicators, Major/Minor alarm LEDs, Reset PWR button, CRT port
• Rear I/O Sled Ports: STDM 1/DATA 1, STDM 2/DATA 2, STDM 3/DATA 3, STDM 4/DATA 4 (DB25); FAC 1, FAC 2 (DB25); CRT; EXT MODEM; RCLAN; EXT TMG — all DB25 connectors
• Rear also features: 50-pin telco Voice/Fax Bands 1–6 connector, six RJ-45 Voice/Fax Band ports, alarm terminal block (Major/Minor, ALo/COM), INT MODEM and RCU connectors
• Rack ears included

Applications

The AT&T RLX-246 was designed for enterprise and carrier WAN environments of the late 1980s and early 1990s, where organizations needed to consolidate mixed voice, fax, and data traffic over a single digital link rather than provisioning separate circuits for each. Packet multiplexers of this type were deployed at branch offices, corporate campuses, and telecom central offices to maximize utilization of leased T1 and fractional T1 lines. The RLX-246 was part of AT&T's Netrix intelligent networking platform, a system aimed at giving network managers centralized control and visibility over multi-location WAN topologies. The HTDM protocol allowed dynamic bandwidth allocation — idle voice channels could release their capacity back to the data pool, which was a key efficiency advantage over static TDM approaches of the era. Today, units like this are sought by telecom historians, legacy network integrators supporting older AT&T Netrix installations, and surplus collectors. The physical DB25-based data interface and RJ-45 voice jacks reflect the pre-RJ-48C/V.35-breakout cabling conventions standard at the time of manufacture.