Voice Compression for PLAR and Hoot n’ Holler Applications

PLAR (Private Line Automatic Ringdown) or ARD (Automatic Ring Down) are traditional TDM point-to-point, private or leased lines used for instantaneous communication between two phone sets. PLAR/ARD (herein referred to as PLAR) refers to the automatic signaling that causes the remote phone set to ring the moment the local phone set is taken off the hook.

The financial trading community commonly employs this technology to support missioncritical communications between traders, whether they work for a single company within the same building, or between different companies in different locations. A single trader will often have multiple PLARs terminated into a central desktop unit called a ”trading turret”, enabling the trader to instantly access a selection of important clients and colleagues from a single handset.

Similarly, Hoot-and-Holler connections (aka ”Hoot” or ”Intercom”) are dedicated "always on" connections used extensively in the financial community to share market updates and trading orders. Unlike the point-to-point PLAR circuits, however, the phone lines used for Hoot applications are bridged so all connected parties in a given location are receiving the same source messages at the same time. Typically, Hoot circuits are connected to trading turrets with integrated speakers so any communications are broadcast throughout a given location.

Along with the financial industry, Hoot and PLAR applications are commonly used to broadcast mission-critical information in news agencies, weather bureaus, public transportation providers, utility companies, manufacturing environments, and elsewhere.

RAD’s Vmux solutions are ideal for organizations looking to establish cost-effective TDM voice communications among multiple offices. Whether establishing a TDM Hoot connection between corporate headquarters and several remote branch offices, or a TDM PLAR between two small branch offices, there is a Vmux solution suited to the situation.

RAD’s central site solution, the Vmux-2100, can support multiple channelized T1/E1 circuits on the network uplink. Using the Vmux’s innovative TDMoIP multiplexing technique and standards-based voice compression you can trunk 4, 8, or even more voice channels of ARD or Hoot over just 64K of TDM bandwidth. Further, since PLAR and Hoot are direct point-to-point (or point-to-multipoint) connections, no switching or call setup is required. These voice channels are generally connected directly to trading turrets or standard phone sets.

The Vmux-110, RAD’s voice trunking gateway for remote locations, is ideal for Hoot applications using an E&M interface over 2 or 4 wire voice channels. The E&M voice ports then connect to speakers to enable the broadcast benefits of Hoot applications. The Vmux- 110 usually sits opposite a central site Vmux-2100 that is connected to a trading system, or a TDM-based bridging device, via T1/E1 voice ports. The central site trading system or another dedicated device performs the bridging of the Hoot lines.

Many large financial service firms have already moved significant portions of their networks to IP backbones to leverage the cost efficiencies of IP networks. Yet many others (financial service or otherwise) have not made the switch due to concerns over return-on-investment and start-up costs.

Given the huge amount invested in functional and reliable TDM-based trading systems and PBX’s (along with their installation and upkeep), organizations are reluctant to replace the equipment without a compelling ROI. Not only would they be abandoning their investment in these legacy systems, but they would also have to underwrite an equally substantial investment to implement native Ethernet/IP turrets and switches. Further, the time-tested feature sets and level of familiarity that end-users have with the TDM- based PLAR and Hoot systems only adds to the level of institutional apprehension. New systems and new technology generally equates to substantial new training costs and learning curve costs. Of course, in the high stakes environment of the financial industry this can have significant, adverse effects on business continuity. The challenge is to reap the gain of IP network convergence without the pain of forklift upgrades.

RAD’s Vmux provides an ideal solution. The VMUX product family supports legacy TDMbased trading systems, whether configured to run over a pure TDM network, or configured to transport TDM traffic over an IP network in pseudowire mode. In either case, the Vmux’s compression and optimization features will reduce the end-user’s operational costs by reducing the number of leased transport lines. End-users who implement a Vmux solution over an IP network benefit further from the cost-efficiencies of the IP network itself, the increased compression and optimization capabilities of the Vmux when running over IP, and from the scale efficiencies of converging their voice traffic and data traffic over a single network.

To represent an on-hook or off-hook state, PLAR/ARD voice channels use CAS or robbedbit signaling (using T1/E1 ABCD signaling bits). Lacking an industry standard signaling protocol for these applications, each vendor uses different sequences of signaling bits to represent these two states. With its transparency to signaling, the Vmux can be configured to interoperate with any trading system regardless of the signaling sequences it uses. This means that the Vmux is not only an excellent voice trunking solution, but also functions as a signaling converter, enabling the seamless integration of disparate trading systems (e.g. IPC and BT Syntegra).

The Vmux solution maximizes the amount of voice traffic that can be transported over available bandwidth, while maintaining the integrity of toll-quality voice and all embedded signaling. This enables organizations to reduce their operational costs by minimizing the amount of bandwidth necessary to trunk all of their PLAR/ARD and Hoot lines without sacrificing the quality of their voice communications. Further, RAD’s Vmux is the ideal solution for organizations seeking to migrate their communications transport medium from traditional TDM networks to cost-efficient IP/MPLS networks while preserving their investment in the quality, feature sets, familiarity, and reliability of their existing TDMbased trading systems.