Monitor Tally Lamps
Many of our rackmount monitors are fitted with "ON AIR" Tally Lamps. These are normally driven from external stimulae, which are generated by events such such as Mixer on air logic, to indicate which channel(s) are routed to line.
The Monitor's tally lamp logic line is designed to be "pulled to ground" by either an "open collector" logic drive, or a discrete contact such as a switch or relay. Users are advised that, although the current sink capability of most logic devices is easily sufficient to provide the 2mA or so current dump requirement, the open circuit potential is circa +12V, which may be excessive for some low voltage Logic Families.
Optionally, several of the monitors can be fitted with multi-colour Tally lamps, which are produced by enabling either a red LED, a green LED, or both (yellow) simultaneously. With multi-LCD monitors, there will be one LED (cluster) per screen; so there are 4 times more wires for a Quad display, for example, than for a single panel. The Wiring schedule shown on the linked PDF, assumes this multi-colour case, but when only red LEDs are fitted, the wiring for the green devices is simply ignored.
© Murraypro September 2009