What is a Telephone Hybrid ?

Telephone hybrids (or telephone balance units, TBUs) provide the interface between professional audio equipment and the public telephone network. They provide protection for your equipment and the public telephone lines, allowing for varying line signals and line conditions. Automatically cancelling out the unwanted signal they also facilitate two-way communication down a single telephone line, converting the two-wire telephone signal to a four-wire send and return signal to be linked to a studio mixer, for example. The hybrid has a telephone line connection and separate terminals for audio input and output from a broadcast mixer, or other professional audio source. A large proportion of Sonifex hybrids are used in radio and television broadcasting applications for allowing external callers to be connected to the studio mixing console. Most of the other units are supplied to communication operations for allowing extremely effective conversion between four-wire audio circuits and standard telephone lines. Built to a very high specification, the DHY-03 is simple to install and automatically adapts to line conditions and programme content.

The Digital DHY-03 Telephone Hybrid is probably the best performing digital hybrid in the world, with simply stunning line balance rejection figures. For the best sounding audio calls you’re likely to hear, you should specify the DHY-03.The DHY-03 is a high quality digital telephone hybrid, which is suitable for most general telephony applications and is often used in radio and TV stations, bingo halls and dealing floors. The digital DHY-03 telephone hybrid is the replacement for the DHY-02, which for many years has set the standard as an excellent value, high quality telephone hybrid. The DHY-03 can be used for any application where a clean telephone signal is required and the line is not subject to excessive delay.

The DHY-03 has the following features :

• Fully automatic - adapts to varying line conditions and has automatic signal limiting.
• Fully adaptive echo cancellation to 127msec - default is 24msec.
• 76dB typical line balance rejection offering superb performance and crystal clear audio.
• Front panel input and output gain controls.
• Front panel LED metering of receive and send signals.
• Built-in conferencing for 2 hybrids, so that a single telco channel on a mixing desk can receive 2 calls.
• Integrated ring detector - automatic call answering after a pre-determined number of rings.
• Automatic call disconnection. Fitted with K-break, line polarity reversal and dial tone disconnect detection, defined by the country selection.
• Automatic ducking facility allows the talent to ‘shout-down’, or talk over, a caller by reducing the gain of the caller’s signal if it goes above a certain level.
• Local and remote line hold switching - calls can be remotely switched through a mixing console.
• Line hold/release button to control line hold circuit, illuminates to indicate the status of the line and flashes to show ring status.
• DTMF tone recognition allowing a opto-isolated GPI output to be made on receipt of selected DTMF tones, e.g. for starting a studio automation recorder automatically to record a remote telephone interview.
• International operation with built-in configurable settings for each country. Country selection allows the unit to provide line impedance and a simulation circuit to match the country.
• RS232 serial port for remote control of the TBU, DTMF tone dialling and firmware upgrades to add new country settings.
• Remote port distributes the remote line connect switch and tally output, a momentary/latch selector and the DTMF detect output.
• The remote line connect switch can be either momentary or latching in its action.
• Balanced mic/line input - 10k balanced input selectable for 0dBu clean feed line, or microphone level with adjustable gain.
• Balanced output - 0dBu low impedance balanced output, with output gain settings.
• Record output - the conferencing output can be set via a jumper to give a mix of the caller and mic/line input signals for recording both sides of the telephone conversation.
• Line limiter, bandpass filter and output noise gate with preset threshold providing low distortion audio.
• Built in universal power supply between 90V AC and 250V AC, 47-63Hz, IEC mains input.
• ETSI approval compliant with European PTT specifications.