Here is a great circuit you can purchase from me to combine two separate intercom systems together. This "in-Line" adapter can also be used in place of the ubiquitous "IL-19". I fit this circuit into a small (3.5"X1.5"X1.5") aluminum box filled with epoxy. The epoxy makes the internal components rock solid for extended life.
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This intercom adapter is real handy for touring rock shows that tie into house intercom systems every night to call spotlight Cues. The arena can keep it's own intercom base station turned on, use their own headsets and beltpacks and deal with their own noise and bad cable problems without causing any interference with the touring intercom system. As long as you place this isolation transformer between your road system and the house system, they are completely transformer isolated! It will also pass 2 channel signals, combine any brand of analog 3 pin XLR systems (ie; RTS to ClearCom, HME to Telex or any combination), and keep system voltages and grounds completely separate.
The capacitors are there to stop any voltage (phantom power, intercom power supply 12V - 48V) from damaging the transformer coils.
Audio Isolation Transformer
Both pin 3 and pin 2 resolve to pin 1 (ground) via the circuit which allows this device to work as an audio terminator. This also allows you to use this adapter as a very clean and efficient line level isolation transformer.
A partial list of places where you can see the ISO Box at work:
Clair Brothers, Cirque du Soleil, Lion King, PRG, Solotech, Creative Technology Inc, Lake Shore AV, Allstate Arena, Auditorium Theater (Chicago), Thunder Audio, ClairGlobal, The Joffrey Ballet, and scores of road technicians throughout the country.
This device has a flat response from 20Hz to 25kHz ± 1.5dB. With a 3dB roll off @ 16Hz!
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