Multiplex communications – Wide area network – Packet switching
Patent
1981-02-26
1983-05-10
Safourek, Benedict V.
Multiplex communications
Wide area network
Packet switching
330263, H04J 320
Patent
active
043833136
ABSTRACT:
A tone generator for a telecommunication--especially telephone--system operating in the PAM/TDM mode comprises two complementary transistors with interconnected emitters joined to a "hot" conductor of a two-wire transmission path forming part of a trunk line between two groups of subscribers, the collectors of these transistors being connected through respective series resistors to a positive and a negative terminal of a DC source. These collectors are further coupled via respective shunt condensers to the "cold" conductor of the transmission path which is grounded through a low-ohmic further resistor. A local oscillator supplies a sinusoidal voltage wave through an operational amplifier to the interconnected bases of the two transistors whereby one or the other transistor conducts upon simultaneous closure, during a time slot assigned to a called subscriber, of a trunk switch at the near end and of a line switch at the far end of the transmission path enabling the resonant discharge of one of the previously charged shunt condensers into a remote line capacitor. Residual energy remaining stored on the parasitic capacitance of the two conductors is dissipated in a subsequent guard interval, upon the reopening of the two switches, as the partly discharged shunt condenser is recharged through the grounding resistor.
REFERENCES:
patent: 2791644 (1957-05-01), Sziklai
patent: 3588366 (1971-06-01), Formenti et al.
Italtel Societa Italiana Telecommunicazioni S.p.A.
Ross Karl F.
Safourek Benedict V.
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