Removed from a TV production control room. Fully operational.

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.

Each telephone hybrid has a telephone line connection, a handset connection and separate terminals for audio input and output from a broadcast mixer, or other professional audio source.

A large proportion of hybrids are used in radio and television broadcasting applications for allowing external callers to be connected to the studio mixing console.

A ringing detector can be used when you need to answer a call automatically, for instance, if a journalist files a report to a PC recorder over a telephone line, the call can be picked up after a set number of rings by the ringing detector.

• Isolated, full-duplex 4-wire interface to direct non-digital telephone exchange lines
• Simple optimization of sidetone rejection with any country's telephone system
• LED indicatiors
• Input level control with line-sensing limiter and limit indicator
• High drive output with level control for direct feed to presenter's earpiece, etc
• Loop-through RJ11 line sockets provide universal connection to line and telephone set
• Connection to the telephone set is maintained while the unit is in use

Audio Specification
Input Impedance - Line Mode (Clean Feed):				10kΩ balanced 0dB
Input Impedance - Microphone Mode:				200Ω balanced
Clean Feed Limiting Input:				+4dBu
Microphone Level Range:				From 74dB to 40dB adjusted by preset pot
Bandwidth to Telephone Line:				250Hz - 4kHz, -3dB ref 1kHz
Telephone Line Impedance:				Nominally 600Ω
Telephone Line Impedance Range:				300Ω to 1500Ω
Output Impedance:				50Ω balanced floating 0dBu
Output Level Range:				+8dB to -14dB adjusted by preset pot
Rejection Ratio:				45dB on 1kHz tone, typically 28dB on complex waveforms, reference peak level of 0dB
Power:				230V 50Hz, or 115V 60Hz. 6W for HY-03.
Connections
Mic/Line Input:				XLR 3 pin female with push button mic/line selection
Line Output:				XLR 3 pin male
Telephone Line:				RJ11 6/4 socket
Telephone Handset/Instrument:				RJ11 6/4 socket