US2515968A - Pulse length measurement - Google Patents

Description

July 18, 1950 J. P. sH 2,515,968

PULSE LENGTH MEASUREMENT Filed May 7, 1947 JOHN P. SHANKLIN Patented July 18, 1950 PULSE LENGTH MEASUREMENT John P. Shanlrlin, Baltimore, Md, assignor to Bendix Aviation Corporation, Towson, Md., a

corporation of Delaware Application May 7, 1947, Serial No. 246,605

Claims. 1

This inventi n i di e ed o elect ca r ays- More specifically it is directed to relays respondin; only o pu ses o ele tr al e gy avi g a preselected width or dur tion.

In s l ctive a ling sy ms, wher in t s sired to ener ize o e of a p ura ity of cir uits f m. a rem point over a s gle ommun ation channel s vera ar an ement e nown- In one of these sys ems. eq ncy sele e tors at the receiving terminal actuate the circuit corr spond n to the req en y o th ei e energy. Another general class of selective calling sys em is that use in the d a l p e y t whe ei th ansmitter prod ce a r s o short electrical ulse an a s eppi g ci cuit at the rec iv end ounts t pulses, a d eo uet s the circui co responding to the .nnmh ro pu received.

It is an object of this invention to proyide a sele tive ca in sys m wh ein le on is made n the as s o puls duration rathe han pu se count as in he teleph ne sy tem It will h ma if t th t the n tant nven ion may he n either to multiply the number of channels available in either the requency e c e o he countin syste s, or al n as a s p e p lyha nel arra gem nt.

This object is a aine by h use of e plura ty of relay and tim elay circuit h re n a first relay is en r ze when it ceives a p se hay reate u a ion tha a red er in d minimum, and a seco d re ay prevents the fir f om operating if the pulse has greater duration than a p e t min d maximum- Other and further objects and advanta es will more fully appear from the following detailed .description when the same i read in connection with the accompanying drawing wherein there is illustrated a pulse-duration selective relay systern in accordance with the instant invention.

Referring now to the accompanying drawing,

nal of a battery 16. The remaining terminal .of

the batte y t is conn cted throug a orma y closed switch it! and hrou h a pair o n rmallyclosed contacts on a relay contact assembly It; to the junction of the resistor ii and the coil I: ,3 second set of contacts. no mally-op n. on the assembly i8 is arranged to close a circuit shorting the coil l2 when the coil l9 associated therewith energized. One terminal of the coil i9 is com nected to ground, and the other terminal is connected to the input terminal Hi through a re sistor 21!. A condenser 2| is connected in shunt with the coil iii. The junction of the resistor H and the coil 12 is connected to ground through a series circuit comprising a resistor 22 and a relay coil 23, and a condenser 24 is connected between the junction of the resistor 22 and the coil 23 and ground. A set of switch contacts 25 is associated with the relay coil 23, and may b neoted as control terminals to an external circuit.

In operation signal pulses of various durations, but having constant amplitude, are applied to the input terminals l0, M. The resistor H and the condenser is form a delay circuit so that input signals will not energize the coil l2 sufficiently to close the contacts I5 unless they exceed a minimum duration 231 which, by way of example, can be taken as two seconds. Similarly the re sistor 20 and the condenser 21 form a second delay circuit so that input signals will not energize the coil E9 sufficiently to operate the contact assembly 18 unless they exceed a second, greater, duration i2 such as three seconds. The coil 23 is connected in shunt with the coil l2 through delay network comprising the resistor 22 and the condenser 24, so that the contacts 25 will not be energized unless energizing current passes through the coil I2 for a third minimum .dura tion is which, can be taken as four seconds.

If a pulse having a duration less than t1, 252, or ii is applied to the input terminals it can be seen that none of the relays will operate, and the entire circuit will remain in a lie-energized state.

If a pulse having a duration greater than 161, but less than t2 or is is applied to the input terminals it can be seen that the contacts 15 will close, and current from the battery 1-5 will flow through the switch assembly l8 and will hold the coil 12 in an energized condition regardless of the eventual cessation of the pulse. After the battery current has energized the coil for a time ti such that t1+t4=t3, the coil 23 will operate the switch 25, and the external circuit will be actuated. The battery will hold the coils l2 and 23 in an energized tate until the switch H is manually opened to reset the system. The coil :9 is energized from the battery when the system is in the locked-on state, but insuflicient current flows through the coil 19 to actuate the contact assembly l8 because of the voltage drop through the resi ors H an 20 whi h included in the series circuit. Relay coil 23 cannot be operated solely by a signal pulse of a duration less than Ta because of the long time constant of the circuit comprising the components II, 13, 22 and 24. Pulses of sufilcient duration to cause coil l9 to operate switch [8 do not reach coil 23, which is short circuited by operation of the switch.

If a pulse having a duration greater than t2 is applied to the input terminals, the switch contacts l are closed at time h, as before, but the coil I9 is energized sufficiently at time t2 to operate the switch assembly l8, to de-energize the coil l2. This action takes place before the coil 23 has become suificiently energized, and no effeet i produced in the external circuit.

Thus, by proper choice of the various time constants it can be seen that the above-described circuit will select pulses having a duration between predetermined limits, and will be unaffected by signals not included in that range. Similar arrangements having difierent time constants may be connected to the same set of input terminals so that a plurality of output circuits may be controlled from a single communications circuit.

The use of electron tubes at one or more points in the circuit to increase the efiicacy of the system may be advisable if greatest accuracy is to be attained. Inasmuch as relays are shown for purpose of illustration only, vacuum tube, or thyratron circuits may be used without departing from the scope and spirit of the invention.

What is claimed is:

1. In a pulse-responsive electrical relay system: a first relay having a first time constant circuit operatively associated with the energizing coil thereof; a second relay having a second time constant circuit operatively associated with the energizing coil thereof; a third relay having a third time constant circuit operatively associated with the energizing coil thereof; a source of pulse signals of differing durations; and a source of relatively constant voltage; circuit connections from said source of pulse signals through said first time constant circuit to said first relay coil; circuit connections from said source of pulse signals through said second time constant circuit to said second relay coil; whereby said first relay is momentarily actuated by pulse signals having a duration greater than a preselected minimum, and said second relay is momentarily actuated by pulse signals having a duration greater than a preselected maximum; switch means associated with said first relay whereby a holding current derived from said source of constant voltage is applied to the said first relay coil during the interval between the actuation of said first and second relays; switch means operated by the actuation of said second relay to disconnect said source of constant voltage from said system; and circuit connections between said first relay coil and said third relay coil including said third time constant circuit applying current from said source of constant voltage to said third relay whereby said third relay is actuated if said first relay coil is ener gized by said holding current for a period of time greater than a second preselected minimum.

2. In a pulse-responsive electrical relay system: a first relay having a first time constant circuit operatively associated with the energizing coil thereof; a second relay having a second time constant circuit operatively associated with the energizing coil thereof; a third relay having a third time constant circuit operatively associated with the energizing coil thereof; a source of pulse signal of differing durations; and a source of relatively constant voltage; circuit connections from said source of pulse signals through said first time constant circuit to said first relay coil; circuit connections from said source of pulse signals through said second time constant circuit to said second relay coil; wherei by said first relay is momentarily actuated by pulse signals having a duration greater than a preselected minimum, and said second relay is momentarily actuated by pulse signals having a duration greater than a preselected maximum; switch means associated with said first relay whereby a holding current derived from said source of constant voltage is applied to the said first relay coil during the interval between the actuation of said first and second relays; switch means operated by the'actuation of said second relay to disconnect said source of constant voltage from said'system'; and circuit connections between said first relay coil and said third relay coil including said third 'time'constant circuit applying current from said source of constant voltage to said third relay whereby said third relay is actuated if said first relay coil is energized by said holding current for a period of time greater than a second preselected minimum; and a switch associated with said source of constant voltage whereby the said holding current may be manually interrupted.

3. In a pulse-responsive switching system: a first electrically actuated switch having a first control circuit and a first time constant circuit associated with said control circuit; a second electrically actuated switch having a second control circuit and a second time constant circuit as-- sociated with said second control circuit; a third electrically actuated switch having a third control circuit and a third time constant circuit associated with said third control circuit; a source of pulses of electrical energy, said pulses having differing durations; a second source of electrical energy having a substantially constant average amplitude; circuit connections from said source of pulses through said first time constant circult to said first control circuit; circuit connections from said source of pulses through said second time constant circuit to said secondcontrol circuit; the time constants of said first and second time constant circuits being so selected that said first switch is momentarily actuated by pulses having a duration greater than a preselected minimum, and said second switch is momentarily actuated by pulses having a duration greater than a preselected maximum; circuit connections including said first and second switches whereby a holding current derived from said second source is applied to said first control circuit during the interval'between the actuation of said first and'second switches; circuit connections including said third time constant circuit between said firstand third control circuits applying current from said second source of energy to said third control circuit when said holding current is applied to said first control circuit, the time constant of said third time constant circuit being so selected that said third switch is actuated if said first switch is ener gized by said holding current for a period of time greater than a preselected minimum.

4. In a pulse-responsive switching system: a first electrically actuated switch having a first control circuit and a first time constant circuit associated with said control circuit; a second electrically actuated switch having a second control circuit and a second time constant circuit associated with said second control circuit; a third electrically actuated switch having a third control circuit and a third time constant circuit associated with said third control circuit; a source of pulses of electrical energy, said pulses having differing durations; a second source of electrical energy having a substantially constant average amplitude; circuit connections from said source of pulses through said first time constant circuit to said first control circuit; circuit connections from said source of pulses through said second time constant circuit to said second control circuit; the time constants of said first and second time constant circuits being so selected that said first switch is momentarily actuated by pulses having a duration greater than a preselected minimum, and said second switch is momentarily actuated by pulses having a duration greater than a preselected maximum; circuit connections including said first and second switches whereby a holding current derived from said second source is applied to said first control circuit during the interval between the actuation of said first and second switches; circuit connections including said third time constant circuit between said first and third control circuit applying current from said second source of energy to said third control circuit when said holding current is applied to said first control circuit, the time constant of said third time constant circuit being so selected that said third switch is actuated if said first switch is energized by aid holding current for a period of time greater than a preselected minimum; and a fourth switch associated with said second source whereby said holding current may be interrupted.

5. A pulse responsive electrical relay system comprising a first, a second and a third relay, a respective time constant circuit associated with each of said relays, a source of pulse signals, means applying signals from said source to said relays by way of said time constant circuits, a source of constant voltage, a switch operable by said first relay to connect said source to said system in a manner to supply holding current to said first relay and to supply current to said third relay by way of its time constant circuit, a switch operable by said second relay to disconnect said source of constant voltage from said system, the time constants of said respective time constant circuits being so selected that said first relay is operated in response to a pulse of a selected minimum duration, said second relay is operated in response to a pulse of a selected duration reater than said minimum duration and said third relay is operated in response to a pulse of said minimum duration plus the application thereto of current from said second source, for a total time which exceeds the response time of said second relay.

JOHN P. SHANKLIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,968,078 Hershey July 31, 1934 2,094,733 Byrnes Oct. 5, 193'? 2,389,078 Perry Nov. 13, 1945

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