RS-232 Datacom Multiplexers & Sharing Devices
RayTel TEL-NPPS Non-Powered Port-Sharing (NPPS) Device

This simple self-Powered Serial Port Sharing device allows a single RS232 host (DTE) device to broadcast information to two RS232 sub-channels (DCE).

• Serial Port Sharing - allows two RS-232 devices to share a single master port.
• Non-Powered - derives ultra-low power from RS-232/V.24 interface signals (minimum 6 VDC at 8 mA).
• Speeds - Up to 19,200 bps (Synchronous Rates1200, 2400, 4800, 9600 and19,200 bps.
• Expandable - supports additional sub-channels via series connection.
• Transparent Operation - operates transparently to both system and data (no impact on data format or system protocols).
• Contention - subchannels contend for the main channel via Request to Send (RTS) and Data Carrier Detect (DCD) activation prevents data collisions between sub-channels. These control lines are used to manage who is allowed to "speak".
• Sync./Async. - supports synchronous and asynchronous communications.
• Internal Clock - for synchronous operation.
• Applications - SCADA and industrial control systems and legacy data communication applications.

The RayTel (Raymar-Telenetics) TEL-NPPS Non-Powered Port-Sharing Device enables multiple serial devices to share a single master communication port in multipoint environments.

Designed for legacy RS-232/V.24 systems, the NPPS allows two modems (or equivalent devices) to connect to a single host port without requiring external power.

The device operates transparently to both system and data, making it ideal for synchronous and asynchronous communication applications.

It intelligently manages contention between connected sub-channels, ensuring that only one device transmits to the main channel at a time while broadcasting outbound data to all sub-channels in parallel.

Power is derived directly from standard RS-232 interface signals, eliminating the need for external power supplies and simplifying installation.

The main channel continuously broadcasts outgoing data to all connected sub-channels.  Sub-channels compete for access to transmit data using RTS/DCD signaling or Data-driven contention, towards the main channel.

If RTS/DCD (data) is raised, the sub-channels transmit data and controls are connected to the main channel. When RTS/DCD (data) drops, control circuitry is switched to monitor both subchannels.  On the NPPS, disconnection occurs immediately after DCD drops or the transmission of 16 idle bits (switch selectable).