Abstract:
An automatically sequenced signal utilizing cross-coupled monostable multivibrators to provide a signaling sequence on time, off time and a total sequencer on time, thereby permitting a coded sequence signal to be transmitted. The timing interval of the multivibrators may be varied over a predetermined range.

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates broadly to a signaling system, and in particular to an automatically sequenced signaling system. 
     The prior art signal generator generates a ringing tone continuously from the beginning of its ringing operation to the end of its ringing cycle. Recently, two-step type tone generators have been used which are adapted to generate, for a predetermined period of time from the time of initial ringing, a low frequency ringing tone, a low level ringing tone or an intermittent ringing tone and thereafter to generate a continuous ringing tone. Heretofore, most of these two-step type ringing tone generators have been operated through the provision of mechanical means. Consequently, they have the disadvantages of being complex in structure, difficult in manufacture, and quite apt to become faulty after very little use. 
     At the present time, small towns and many civilian and military complexes utilize a sequentially coded signal, in the form of a siren or bell or the like, to signal a predesignated area or district in which the problem exists. Such type of system is generally utilized for fire distress situation. 
     When fire alarm is requested, someone must manually hold a switch down for the prescribed fire alarm signal. This system requires that the operator time the desired signal. If the operator is busy with the alarm system, he is not available to answer the phone and give directions, or to notify the Commander, etc. The present system has caused problems because of interpretation of required signal. The present invention provides an automatically sequenced signaling system that sounds an automatic signal for a precise time interval. 
     SUMMARY OF THE INVENTION 
     The present invention utilizes monostable multivibrators in a cross-coupled arrangement to establish a sequence range of a predetermined time interval. A timing circuit is used in conjunction with the various multivibrator pairs to provide a plurality of signal sequencing combinations. The signal sequencing is accomplished by using two cross-coupled 74121 monostable multivibrators which give a sequence range of 40 ns to 40 sec depending upon the resistance and capacitance used. The first monostable is set for the on time and the second for the off time. Along with the monostable there are two 555 IC timers which control the total sequencer on time. The unit is manually operated by turning it on, selecting the proper sequence, placing the auto-manual switch to auto, and then pressing start. 
     It is one object of the present invention, therefore, to provide an improved automatically sequenced signaling system. 
     It is another object of the invention to provide an improved automatically sequenced signaling system wherein one of the plurality of sequenced signals is automatically provided. 
     It is another object of the invention to provide an improved automatically sequenced signaling system wherein an automatic signal with a precise time interval is achieved. 
     It is yet another object of the invention to provide an improved automatically sequenced signaling system wherein the alarm signal is automatic in time and frequency, thereby eliminating confusion and inconsistency in signaling. 
     These and other advantages, objects and features of the invention will become more apparent after considering the following description taken in conjunction with the illustrative embodiment in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1a, 1b are a block diagram, shown in partial schematic form of the automtically sequenced signaling system according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the FIG. 1a, there is shown an automatically sequenced signaling system for achieving the automatic sounding of an alarm which may comprise a particular signaling sequence or coded signal. The signaling system utilizes a power supply circuit 10 to provide the necessary voltages for system operation. A control unit 12 includes a start switch 5 to permit an operator to initiate the automatic signaling sequence. The multivibrator unit 14 comprises a pair of cross-coupled monostable multivibrators, IC2, IC3 to provide a sequence range of 40 nano-seconds to 40 seconds depending upon the system requirements. The multivibrator units 15, 16, respectively, comprise integrated circuits IC4, IC5 and IC6, IC7 to each provide a sequence range of 40 nano-seconds to 40 seconds. The integrated circuits IC2 through IC7 are 74121 integrated circuit units and are utilized to determine the system on-time and the off-time. Two timing units 17, 18 which respectively are comprised of integrated circuit units 555, are utilized to control the system total sequencer on time. It may be noted that points, AA, BB, CC, DD and EE in FIG. 1a are connected to points of the same designation in FIG. 1b to form a total circuit as shown in FIG. 1a and FIG. 1b. 
     Turning now to FIG. 1b, it may be seen that the output of multivibrator unit 14 of FIG. 1a is connected by means of point AA to the first input of nand gate G4. The outputs of multivibrator units 15, 16 are respectively connected through points BB, EE to the first input of nand gates, G5, G6, respectively. The timing unit 17 of FIG. 1a is connected by means of point CC to the second input of both nand gates G4, G5. The timing unit 18 of FIG. 1a is connected by means of point DD to the second input of nand gate G6. Switch S4a, S4b is a two wafer ganged rotary switch with at least seven positions thereon. Switch position 1 of switch S4a-b is the off position. Position 2 of switch S4a is connected to the output of nand gate G4. Position 3 of switch S4a is connected to the output of nand gate G5. Positions 4 and 5 of switch S4a and position 5 of switch S4b are connected to each other and to the output of timing unit 17 of FIG. 1a through point CC. Position 6 of switch S4b is connected by means of point DD to the output of timer unit 18 of FIG. 1a. Position 7 of switch S4b is connected to the output of nand gate G6. The rotary arms of switch S4a,b are respectively connected to the input of gates G7, G8 both of which are respectively connected to +Vcc by resistors R 20 , R 21 . The output of nand gate G7 is connected to buffer unit I1 which one-sixth of integrated circuit IC12, a hex buffer with open collector, high voltage output. Buffer unit I1 is utilized as a relay driver for relay unit K1. When relay unit K1 is activated, the switch contact therein is closed and the klaxon (not shown) is sounded through switch S2 in the auto position when switch S4a is in position 2 through 5. Buffer unit I2 is the relay driver for relay unit K2. When relay unit K2 is activated, the switch contact therein is closed and the siren (not shown) is sounded through switch S3 in the auto position, when switch S4b is in positions 5 through 7. 
     The automatically sequenced signaling system operates in the following manner. The signaling sequence and the total interval time is established by a pair of monostable multivibrator integrated circuit (IC) chips, and the 555 IC timers. The 555 IC may be used as a one shot, free running or gated oscillator. It may be operated with a Vcc source of 4.5 to 16 volts. The timing range may be set from microseconds to hours. It has an adjustable duty cycle which is accomplished by external resistive-capacitor (RC) networks, R12, R13, C8 and R14, R15, C9, respectively connected across Vcc and pin 6, threshold (TH) and discharge (DS) pin 7. 
     The 555 IC&#39;s in this sytem are adjusted for the total on time. The integrated circuit, IC 6 controls the total on time for integrated circuits IC&#39;s 2, 3, 4, 5. The integrated circuit IC 7 controls the on time for integrated circuit IC 8 and 9. The following equation is used to determine the on time for this system. 
     
         ______________________________________D = Duty cyclet.sub.1 = High outputt.sub.2 = Low outputR = ohmsC = farads ##STR1##t.sub.2 + 0.693 (Rb × C)T = 0.693 (Ra + 2Rb) × CIn the present example:Ra = Resistors R12 &amp; R14, Rb = Resistors R13 &amp; R15C = Capacitors C8 &amp; C9T.sub.1 = 0.693 (1000 + 1 × 10.sup.6) × .000470= 326 seconds or 5.4 minutes (high)______________________________________ 
    
     The system was adjusted for the following signals. Switch S4a,b selects the proper signal. Switch S5 is the start button. Switch S4a,b is in the switch position number as shown below: 
     
         ______________________________________1. Off2. Fire Housing Area        3 Min Long                  5     Sec Intervals                                 Klaxon3. Fire Operations        3 Min Long                  10    Sec Intervals                                 Klaxon4. Fire Squadrons        3 Min Long      Steady   Klaxon5. MARE      3 Min Long      Steady   Klaxon &amp;                                  Sirens6. Recall    5 Min Long                  10    Sec Intervals                                 Siren7. Shelter   5 Min Long                  3     Sec Intervals                                 Siren______________________________________ 
    
     The integrated circuits are adjusted as follows: 
     
         ______________________________________IC 6            3     Minutes On (High)IC 2 &amp; 3        5     Seconds On/OffIC 4 &amp; 5        10    Seconds On/OffIC 7            5     Minutes OnIC 8 &amp; 9        3     Seconds On/Off______________________________________ 
    
     The integrated circuits IC 2 and 3 are 74121 monostable multivibrator transistor-transistor-logic (TTL). The 74121 IC&#39;s are Schmitt circuitry, cross connected to flip-flop on and off at the desired sequence. The integrated circuits IC&#39;s 2 and 3 are examples of the other circuits, IC 4, IC5, IC8, and IC9. 
     The integrated circuit IC 2 is adjusted for the on time and integrated circuit IC 3 is adjusted for the off time to give an interval signal to nand gate G4. The integrated circuit IC 2 has pins 4 and 5 connected to +5 volts Vcc. This puts pin 5 as a high input to an and gate. Pin 4 is a high input to an OR gate. Pin 3 of integrated circuit IC 2 is cross connected to pin 6 of IC 3 which is a low output. With a high on pins 4 &amp; 5 and a Low on pin 3, the or gate output is high to the and gate. With a high on pin 5 and a high from the or gate gives a high input to the multivibrator S input. The multivibrator which is part of the 74121 integrated circuit has an S and an R input. The S input to the multivibrator is an internal connection that is not accessible to an external IC pin. The R input is connected to IC pin 11 on all 74121 integrated circuits to provide external accessibility. The RC circuitry is connected to the R input through pin 11. The output of the multivibrator in the integrated circuit IC3 is high at pin 1 and low at pin 6, which is cross connected to the other multivibrator in the integrated circuit IC2. 
     The output of integrated circuit IC 3, pin 1 is high and connected to input one or the A1 side of G4 a 7400 IC nand gate. The input 2 or B1 side of the nand gate is connected to pin 3 of integrated circuit IC8, the 555 timer. The high&#39;s on gate G4 enables a low output to gate G7. Gate G7&#39;s output is a high to integrated circuit IC 12 a 7406 not gate or hex buffer unit. Buffer unit I1 which is part of integrated circuited IC 12 allows relay K1 to energize and the klaxon to sound. 
     All components of this system are off-the-shelf items. All digital integrated circuits utilize different components to accomplish the required logic. DTL use diode-transistor logic, TTL use transistor-transistor-logic, RTL use resistor-transistor-logic and CMOS are complementary metal oxide-silicon devices. 
     There is shown in Table I typical values for the components used in the present example: 
     
                       TABLE I______________________________________Component          Value or Description______________________________________Transformer T1     16VCT 640maDiodes D1-D2       IN4002Capacitor C1       2500 μf 15V ElecCapacitor C2       1 μf 6V TantalumCapacitor C3       47 μf 50V ElecCapacitorsC4-C11             470 μf 16V ElecC12-C23            .05 μf disc (Vcc to              Gnd on each IC)Resistor R1        10KResistorsR2,R3,R20,R21      2.2KR4,R5,R8,R10,R16,R18              2KR5,R7,R9,R11,R17,R19              50K trimpotR12,R14            1KR13,R15            1M trimpotIntegrated CircuitsIC1                7805IC2-IC5, IC6-IC7   74121IC12               7406IC8-IC9            555IC10-IC11          7400______________________________________ 
    
     Digital integrated circuits are identified by numbers such as 7400 which has four nand gates. Each manufacturer adds letters to the basic numbers plus letters to describe speed and package type. Example, 74S00 is a slow speed device, and a 74H00 is a high speed type. The 74LS00 is a low power Schotky integrated circuit which utilizes diode input in place of transistors. Manufacturers add letters to linear circuit devices also. There are no difference to the logic of any of the devices. 
     
         ______________________________________IC#       IC Unit   Circuit Function______________________________________IC 1      7805      Voltage regulator               Provides a steady voltage that is               unaffected by changes in supply               voltage as long as the supply               voltage is above the desired output               voltage.IC 2, 3,  74121     Monostable Multivibrator4, 8, 9IC 6, 7   555       Timer               Operates as a one shot or a stable               multivibratorIC 10, 11 7400      Quad 2 input nand gateIC 12     7410      Hex Buffers with open collector,               high voltage output______________________________________ 
    
     The power supply for this system utilizes a step-down transformer, T1. The primary voltage is 117 volts and the secondary can be 12 to 16 volts center-tapped, at 1 amp. Diodes D1 and D2 rectify the secondary voltage. Capacitors C1 and C2 are used as filters, to smooth the rectified voltage. The integrated circuit IC 1 is a 7805 voltage regulator that provides a steady +5 volts output and is unaffected by changes in supply voltage. 
     Although the invention has been described with reference to a particular embodiment, it will be understood to those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claims.