MIXED SIGNALS
Many telephony players continue to buck the SIP trend, on both the PBX and handset fronts, preferring to implement proprietary, IP-based signaling protocols, ostensibly to support their systems' unique features.
Among handset vendors, Hitachi supports SIP, while Vocera is limited to a proprietary signaling protocol. SpectraLink does offer versions of its devices with SIP support, but you'll sacrifice some functionality.
SpectraLink entered the market prior to SIP becoming popular for telephony. The company's business goal was to enable mobile telephony for enterprises, so it had to meet enterprises where they were at the time--running PBXs with proprietary digital and analog interfaces. On the PBX-facing side, the company emulated a digital handset, while on the IP side, SpectraLink wrote its own signaling protocol, SRP (SpectraLink Radio Protocol) and standardized around the compressed ADPCM (Adaptive Differential Pulse Code Modulation) codec, rather than the more common G.711.
Vocera uses proprietary signaling to enable voice-driven hands-free communication. It has not pursued reseller relationships in the same way that SpectraLink has with PBX manufacturers, and doesn't license its protocol, as Cisco does. Of course, Vocera doesn't offer a generic handset, and it isn't seeking to enable generic device access to its system software; more important to it are form factor, weight and audio capabilities.
Hitachi has the first enterprise-grade SIP-based wireless handset and claims a customer with more than 7,200 deployed devices (see our take on Hitachi's Wireless IP5000 at nwcreports.com). At Interop 2006 in Las Vegas, SpectraLink demonstrated its regular Wi-Fi handset with a SIP software load working against the Asterisk PBX. Unfortunately, that implementation still requires the SVP gateway for proprietary QoS. The good news is, SpectraLink is becoming more SIP-friendly in response to market demand. Cisco declined to license Skinny with SpectraLink's new NetLink 8000, so SIP will be the signaling protocol with Cisco's Unified CallManager.
SpectraLink also plans to target small-biz VoIP installations that may be using SIP-based PBXs such as Asterisk, Pingtel or Mitel. Ironically, however, SpectraLink discouraged us from using SIP against our Asterisk PBX in our most recent review.
Cisco has added SIP support in the latest version of its Unified CallManager and on a few desk phones, but the company does not support SIP on its popular 7920 handset. As for its newest handset, the 7921G, the company's FAQ states that support for SIP will come later.
Vocera is in a unique position because its value is not exclusively in the handset per se, but also the software on its app server that supports voice commands, unique call features such as call escalation, and can tie into third-party communication systems and apps.
