Our recent work on the regioselective synthesis of a number of heterocycles (4) prompted us to search for a simple and effi- cient reagent for this heterocyclization. We have recently achieved a facile entry to this ring system 6 (5) with the use of a well-known brominating agent, pyridine hydrobromide per- bromide, which we report here.
Voice VLAN. 1  Voice VLAN allows you to enhance VoIP service by configuring ports to carry IP voice traffic from IP phones on a specific VLAN. VoIP traffic has a preconfigured OUI prefix in the source MAC address. 2  You can configure VLANs on which voice IP traffic is forwarded.
From Wikipedia, the free encyclopedia. A voice frequency (VF) or voice band is one of the frequencies, within part of the audio range, that is used for the transmission of speech. In telephony, the usable voice frequency band ranges from approximately 300 Hz to 3400 Hz. It is for this reason that the ultra low frequency band of the electromagnetic spectrum between 300 and 3000 Hz is also referred to as voice frequency, being the electromagnetic energy that represents acoustic energy at baseband.