INSTALLATION FOR SUCCESSIVELY TRANSMITTING A CALL SIGNAL FROM A PLURALITY OF TRANSMITTERS IN TURN

• US 3,743,937 A
• Filed: 10/05/1971
• Issued: 07/03/1973
• Est. Priority Date: 10/14/1970
• Status: Expired due to Term

• Current Assignee: Pierre Saillard
• Original Assignee: Pierre Saillard
• Inventors: Saillard, Pierre
• Primary Examiner(s): Mayer, Albert J.
• Application Number:
  US05/186,670
• Time in Patent Office: 637 Days
• Field of Search: 325/53-55,51,52,4,184,2,6,9,11,13,14,166,169,186,64,187,1 343/180,228,227 340/186,211 179/17R
• US Class Current: 341/174
• CPC Class Codes: G08B 3/1016 using wireless transmission calling systems using transmission by inductive loop H04B5/00

Abstract

A central call station is connected to a plurality of transmitters successively triggered to transmit a high frequency call signal for a predetermined time with each transmitter triggered by the preceding transmitter through connecting wires.

Claims

1. An installation to call a person who is moving along a path and is equipped with a portable radio receiver by utilizing a single high frequency call signal comprising a plurality of transmitters distributed along the path and tuned to transmit successively on the same frequency;

each of said transmitters including generating and transmitting means to generate and transmit the call signal, controlling means connected to said generating and transmitting means to allow the transmission of the call signal for a predetermined time, triggering means connected to all at least one of said above mentioned means to send a triggering signal to said next successive one of said plurality of transmitters to trigger said next successive transmitter for transmission of the call signal upon cessation of transmissions from said above mentioned generating and transmitting means so that two succeeding transmitters transmit the call signal one after the other;

wire connections carrying said triggering signals between said transmitters; and

a means to trigger the transmission in a first one of said transmitters to initiate transmission in the installation.

2. An installation according to claim 1, further characterized by said wire connections including connection means connecting said triggering means from the last of said transmitters operating in succession to the first of said transmitters in the sequence of operation.

3. An installation according to claim 1, further characterized by said triggering signal of each of said transmitters is transMitted by said triggering means of that transmitter as soon as that said transmitter ceases to transmit the call signal.

4. An installation according to claim 1, further characterized by said means to trigger the transmission in a first one of said transmitters being a central call station having means to trigger the operation of said first of said transmitters in the sequence of operation with a signal having a recurrence period of a value at least equal to the sum of the operating times of all of said plurality of transmitters of the call system installation.

5. An installation according to claim 1 further characterized by said means to trigger the operation of said first of said transmitters transmitting a single signal from said central call station.

6. An installation according to claim 1, further characterized by each of said transmitters further including a voltage supply source, said generating and transmitting means including an oscillator connected to said supply source, and said controlling means including a normally open switch connected to said triggering means of the preceding transmitter in the sequence of operation of said transmitters.

7. An installation according to claim 6, further characterized by said wire connections including connection means connecting said triggering means from the last of said transmitters operating in succession to the first of said transmitters in the sequence of operation;

said connection means including a conductor and a switch element connected in series between said normally open switch of said last of said transmitters operating in succession and said triggering means of said first of said transmitters in the sequence of operation.

8. An installation according to claim 1 further characterized by a common reference potential connection to all of said plurality of transmitters;

a supply source in each of said transmitters;

said generating and transmitting means in each of said transmitters including an oscillator connected to said supply source;

said triggering means including a normally open switch in each of said transmitters connected between said oscillator and said common reference potential connection;

said normally open switch having a point connected to a control means in the succeeding transmitter in the sequence of operation of said transmitters, said triggering means producing a triggering signal by the rise in potential in the attached said wire connection resulting from the opening of said normally open switch.

9. An installation according to claim 1, further characterized by said triggering means including an input circuit having an input transistor connected to one of said wire connections coming from a preceding said transmitter, said input transistor being conductive when the potential of the connecting conductor is positive, and an output transistor connected to said input transistor which is conductive when said input transistor is non-conductive and vice versa, a differentiator circuit connected to said output transistor, a detector connected to said differentiator circuit permitting only the passage of the pulses supplied by said differentiator circuit and corresponding to the rise in potential of said wire connection, and a monostable multivibrator connected to said detector circuit, the change of which to the unstable state is triggered by the pulses transmitted by said detector circuit, said multivibrator effecting during its unstable period the closing of a normally open switch of said transmitter connected to said multivibrator by transmission of a pulse from said multivibrator to said switch.

10. An installation according to claim 1, further characterized by each of said transmitters including a self-contained supply source.

11. An installation according to claim 1, further characterized by said means to trigger the transmission in a first one of saId transmitters including a central call station having a common supply source;

a common supply conductor connecting a terminal of said common supply source to all of said transmitters, the other terminal of said supply source being connected to ground;

a capacitor in each of said transmitters connected on one hand to said common supply conductor through a current regulating circuit, and on the other hand to ground by a conductor connected to the frames of said transmitters.

12. An installation according to claim 11, further characterized by said common supply conductor, said common frame conductor, and wire connection between said transmitters included in a screened multiwire cable with said screening constituting an aerial common to all of said transmitters.