Paging intercommunication system
AssigneeJab Company, Inc.
InventorRoger W. Shields
Life of this patent
Estimating the term…
Abstract
Intercommunication between a plurality of stations is established through a pair of signal lines to which portable units are connected, each unit having its own power supply contributing to a low DC operating voltage maintained across the signal lines through which the audio signals are also conducted. Communicate and pager switches associated with each unit respectively control signal connections, d.c. line-voltage level, and signal input impedance for establishing intercommunication and paging functions.
Claims15
In an intercom system having a common signal cable to which a plurality of communication units are connected, each of said units including a source of electrical energy connected to said cable for normally maintaining a relatively low d.c. operating potential thereon, a paging circuit having an output speaker, through which incoming audio signals are reproduced, sensing means responsive to a relatively high d.c. driving voltage applied to the signal cable with said incoming audio signals for connecting the paging circuit thereto to reproduce the incoming audio signals, a communication circuit having input and output transducers through which incoming and outgoing audio signals are respectively reproduced and generated, communicate switch means for connecting the signal cable to the communication circuit and simultaneously disabling the sensing means, and pager switch means interconnected between the signal cable and said source of electrical energy for selectively applying said d.c. driving voltage to the signal cable while the outgoing audio signals are being generated in the communication circuit.
In an intercom system having a pair of signal lines, a communication unit including a pair of batteries connected in parallel between one of the signal lines and ground to apply a relative low d.c. operating voltage to the signal lines, a pair of amplifiers, signal voltage sensing means connected across said signal lines for connecting one of the amplifiers to the parallel connected batteries in response to a higher driving voltage applied to said signal lines, selectively actuated switch means for simultaneously disabling the voltage sensing means and connecting the other of the amplifiers across the signal lines, and pager switch means connected to said batteries for reconnecting one of the batteries between ground and the other of the signal lines to apply said driving voltage to the signal lines.
Dependencies are inferred from the claim text.