strobe is powered from the RTS line but only draws 10 milliamperes. It also supplies a relay closure and a logic signal.
Limitations of Each System
Cable capacitance, resistance, and crosstalk affect all three systems. The longer cables (over 2000 feet) limit the number of belt packs at the end. A system with cumulative cables adding up to 10,000 feet will have a reduction in frequency response due to cable capacitance. Both resistance and capacitance affect crosstalk.
If all you have is a
Some of the information in this chapter is repeated in the next chapter, but in a different context.
Summary
(Some Definitions)
1A
2
3A balanced line reduces unwanted noise and crosstalk pickup.
4A full duplex intercom allows simultaneous
5The human ear perceives a 10 decibel increase as twice as loud.
6A belt pack is a user station designed to be worn on a user’s belt.
7A main station is a multichannel user station.
8A master station combines a user station and a power supply.
9Sidetone is a small amount of microphone signal fed back to the user’s ear.
10Crosstalk is unwanted interference.
(A Short History)
1Television, theatrical, and concert production crews need
2Early intercoms were inflexible and limited to small groups of users and sometimes short distances.
3In the 1970s, fresh new designs were the beginning of the modern
(Present Day Systems and Manufacturers)
1Principal
2With the exception of David Clark, present day
16 H a n d b o o k o f I n t e r c o m S y s t e m s E n g i n e e r i n g
