typically connected to 2-wire party-line circuits. By adding DC power sources to the Model 46’s 2-wire interfaces, the need for external intercom power supplies could often be eliminated.
The final step was to create a physical package that would provide significant re- sources in a form that allowed simple and reliable integration with other equipment. This was accomplished by including two
2-channel interfaces in a one-rack-space enclosure. Using standard 3-pin XLR-type audio connectors would enable rapid installation and troubleshooting. And by making the Model 46 “universally” pow- ered, installation in any locale could be directly supported.
Installation
In this section you will be installing and interconnecting the Model 46. The one- rack-space unit will be mounted in an equipment rack. Audio input, audio out- put, and party-line intercom connections will be made by way of 3-pin XLR-type connectors. AC mains power will be con- nected by means of a detachable cord set that is compatible with the Model 46’s 3-pin IEC 320 C14-type inlet connector.
System Components
The shipping carton contains the Model 46 Interface and associated user guide. Units destined for North America and Japan also include an AC mains cord. Your dealer or distributor should provide an AC mains cord for other destinations.
Locating the Model 46
The Model 46’s mounting location will dic- tate the length of the cable runs needed to
link the unit with the connected devices. This is really only a factor in relation to the 2-wire party-line intercom circuits. These circuits carry unbalanced audio which can be susceptible to interference and crosstalk issues. Intercom circuits also carry DC power which may make resistive losses come into the picture. In general, shorter intercom cable lengths will as- sure more reliable and consistent system performance. Another location criterion is access to the Model 46’s front panel. An optimal location will allow convenient use of the auto null push buttons and easy observation of the status and level meter LEDs.
Mounting the Model 46
Once a mounting location has been se- lected installation can begin. The Model 46 requires one space (1.75 vertical inches) in a standard 19-inch (48.3 cm) equipment rack. Secure the unit into the equipment rack using two mounting screws per side.
4-Wire Audio Inputs and Outputs
Two audio line input and two audio line output signals are associated with the
4-wire section of each of the Model 46’s two interface circuits. Connections are made using standard 3-pin male and female XLR connectors. Refer to Ap- pendices A, B, and C for details on inter- connecting with Telex/RTS, Riedel, and Clear-Com matrix intercom systems.
4-Wire Line Inputs
As previously mentioned, each of the Model 46’s two interfaces allows two analog line-level audio sources to be
