GAI-Tronics Electro Sound Electro-Sound Communication System - Manual (Page 2)

Pub. 42004-072D
Electro-Sound Communications System Page: 2 of 9
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Handsets and headsets contain high-efficiency earpieces, noise-canceling microphones, and integrated
circuit dual operational amplifiers with anti-sidetone circuitry, all to optimize operation in high-noise
environments. The power to operate the handsets and headsets is applied to the same transmission wires
used for talking. The power comes from a power source that features regulated voltage, current limiting,
and a high output impedance.
The addition of one paging control wire to the transmission line, together with a two-way interface
amplifier, allows the system to page into a Page/Party
®
system and support conversation both ways in a
party-line mode.
The addition of one alarm control wire to the transmission line provides an isolated contact closure at the
power source when any alarm connected anywhere along the transmission line is closed.
Power Source
The plug-in power source is powered by 115 volts ac, 50/60 Hz and supplies enough power to operate 15
handsets and/or headsets simultaneously. The output of the supply is regulated to a dc voltage of 8.8 volts
nominal. The output current is limited so that under shorted line conditions the supply will deliver no more
than 275 milliamps. The ac talking voltage, as well as the dc potential, appears across the output terminals
of the supply. The overall size of the power source, including the enclosure, is approximately 8 inches
× 8
inches
× 5 inches deep. More than one power source may be used on one line to achieve long line
connection with low loss.
Wiring that is foreign to the operation of the system shall not be associated in any way with the
interconnection cable or wiring, nor shall it be fed into or through the enclosure or conduit. The enclosure
and conduit shall not be used to ground any other piece of equipment.
Handsets and Headsets
Each handset and headset contains a dual operational amplifier (op-amp). One op-amp boosts the output
of the noise-canceling dynamic microphone up to the level required for proper line transmission; the other
op-amp provides power to the earpiece in sufficient amount for use in high-noise environments. An
anti-sidetone circuit is used in the transmitting amplifier, so that voice and ambient noise signals do not
reach the receiving amplifier of the same handset or headset, while incoming line signals from other
handsets or headsets do reach the receiving amplifier.
The transmitting amplifier is a constant current device, and therefore, the handsets will drain approximately
12 milliamps from the power source even though the line voltage may be down to 3 volts at the end of a
long line.
The headsets are designed to wear with or without a hardhat. They are equipped with a paging switch and
a three-circuit cord and plug. The headsets will operate in a paging or non-paging system without
modification.
Extension Cables
The headsets have short cords, and therefore, require extension cables to allow movement in and about the
area of the jack station. This arrangement also allows a user to disconnect their headset from the circuit
without losing the ear protection in noisy environments. The 30-foot cable has a belt clip 2 feet from the
headset end to prevent any strain from reaching the headset. The cable will readily disconnect from the
headset when undue strain occurs.