US3205315A

US3205315A - Indicator light and control circuit

Info

Publication number: US3205315A
Application number: US196187A
Authority: US
Inventors: Roger C Curtis
Original assignee: Dictaphone Corp
Current assignee: Dictaphone Corp
Priority date: 1962-05-21
Filing date: 1962-05-21
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07

Description

Sept? 965 R. c. CURTIS 3,205,315

INDICATOR LIGHT AND CONTROL CIRCUIT Filed May 21, 1962 ATTORNE Y8 United States Patent 3,205,315 INDICATOR LIGHT AND CONTROL CIRCUIT Roger C. Curtis, New Haven, Conn., assignor to Dictaphone Corporation, Bridgeport, Conn., a corporation of Connecticut Filed May 21, 1962, Ser. No. 196,187 3 Claims. (Cl. 179100.1)

This invention relates to an improved and simplified indicator light and control circuit for a dictating machine and the like.

An object of the invention is to provide an arrangement of this kind which is efiective in operation, yet low in cost.

In a dictating machine, such as the one disclosed in US. Serial No. 728,646 now Patent No. 3,056,606, there is an indicator light on the front panel of the machine which lights when the machine is turned on, the sole function of this light being to distinguish between the on and the off conditions of the machine. There is also another light alongside the first and whose brightness varies in accordance with signal level during recording. This second light glows more brightly when the sound being recorded increases, and less brightly, or not at all, when the signal level decreases. Because the second light does not glow, at least to any appreciable extent, when the machine is on but not in use, it is of course necessary in this prior arrangement to have the first light also. The present invention in one of its aspects provides a single light which is connected in a unique circuit to operate effectively as a combined on-olf, and volume level indicator.

The dictating machine described in the above-mentioned application is turned on by a switch on the machine. Thereafter, it is set in operation, either to record or to play back, by an internal clutch which is remotely controlled through a push-button switch mounted on a hand microphone. The present invention in another of its aspects provides an improved circuit for controlling a clutch of this kind and simultaneously for reacting upon the indicator light circuit to insure maximum brightness of the light when the machine is on but not in operation.

The clutch control circuit provided according to the invention includes an amplifying transistor, the input of which is controlled by the remotely located push-buttton switch. When this switch is closed, output current from the transistor is applied to a solenoid which actuates a clutch inside the machine and sets it into operation. An important feature of this arrangement is that during the initial part of turning on, the transistor applies to the clutch solenoid a large pulse of current to actuate the clutch surely and quickly. Thereafter, the current ap plied is automatically lowered to a much smaller value which is just sufiicient to keep the solenoid actuated.

The indicator light in this new arrangement comprises a single, miniature incandescent bulb or lamp which is connected in the output circuit of a control transistor. The input of this transistor is in turn connected to the audio amplifier of the machine, the connection being such that when there is no audio signal, the indicator light glows its brightest, and when there is maximum audio signal, the lamp glows dimmest (or not at all). Now, to insure that this lamp also provides a reliable indicator that the machine is turned on, a muting transistor is connected to the audio amplifier. This muting transistor is operated by the remote push-button switch, and when the machine is on but not in operation this switch is open. The muting transistor is biased to conduct, thus disabling the audio amplifier. This prevents any audio signal from reaching the control transistor to which is connected the indicator lamp. Accordingly, in this condition the lamp 3,205,315 Patented Sept. 7, 1965 glows its brightest. When the machine is set in operation, a muting transistor is biased off, thereby permitting the amplifier to work in normal fashion.

A better understanding of the invention together with a fuller appreciation of its many advantages will best be gained from the following description given in connection with the accompanying drawing which shows a circuit embodying features of the invention.

The circuit 10 shown in the drawing includes a conventional audio pro-amplifier 12 having an input 14 adapted to receive signals from a microphone (not shown), for example. The output of this unit 12 is fed via a lead 16 to the input of a transistorized amplifier circuit, generally indicated at 18, which for the most part is conventional. This circuit includes a driver transistor 20 and a pair of output transistors 22 and 24 operated in push-pull relationship. The latter in turn applies through a coupling capacitor 26 an amplified audio signal to a recording head, generally indicated at 28. Alternatively, as indicated by the dotted lines, when the circuit is conditioned for playback a loudspeaker 30 is driven instead of the recording head.

Also connected to output transistors 22 and 24 through capacitor 26 and a second capacitor 32 is a control transistor 34. Placed in the emitter-collector circuit of the latter in series with a small value resistor 36 is a combined indicator and volume-level lamp 38. This lamp, as previously mentioned, is placed in the front panel of a dictating machine, or the like where it is easily visible. When no audio signal is being applied to control transistor 34, lamp 38 will shine with maximum brightness. Conversely, with maximum audio signal, the lamp will be dimmest.

T o mute amplifier circuit 18, and to prevent audio signals from being applied to the control transistor except when desired, i.e. during recording, input lead 16 is bypassed to ground by a muting transistor 40. When conducting, this transistor acts as a short-circuit across the input to transistor 20. When not conducting, muting transistor is effectively an open circuit and transistor 20 can receive audio signals from pro-amplifier 12.

The control of muting transistor is effected through a lead 42 and a resistor 44 whose lower end is adapted to be grounded through a switch 46. The latter is, for example, a push-button switch mounted on a hand microphone of a dictating machine and by which the machine is set to record. When switch 46 is closed, lead 42 will have its biasing voltage lowered, thus increasing the effective resistance of transistor 40 to a point where it no longer has any effect on the amplifier circuit. Simultaneously, switch 46 turns on an amplifying or switching transistor 48. The latter, or a brief interval, determined by the time constant of a capacitor 50 and resistors 52 and 54, serves as a low resistance path from the positive voltage lead (-1-) to a clutch solenoid coil 56 whose lower end is now grounded by switch 46. After a short time, even though switch 46 remains closed, transistor 48 will turn off leaving coil 56 connected to the positive lead by a resistor 58. The value of this resistor is such that the clutch solenoid will remain properly energized with minimum circuit until switch 46 is again opened. When the switch is opened, coil 56 of course will be de-energized. Also, the voltage on lead 42 will become more positive thereby making muting transistor 40 very low in resistance. In this condition, though the drive motor of the dictating machine is running, the machine will not be recording and indicator light 38 will shine brightly.

The above description is intended in illustration and not in limitation of the invention. Various minor changes or modifications in the embodiments set forth may occur to those skilled in the art and these can be made without departing from the spirit or scope of the invention as set forth.

I claim:

1. In a dictating machine having means for amplifying electrical voice signals input to said machine, an indicator lamp, means for causing said lamp to burn with a relatively high initial intensity when said amplifying means supplies no output signal, and when an output signal is supplied by said amplifying means, to burn with an intensity lower than said initial intensity by an amount dependent upon the magnitude of said output signal, a solenoid-operated drive clutch, and means for energizing the solenoid of said clutch, the improvement of means for disabling said amplifying means and thereby causing said lamp to burn with said high initial intensity when said solenoid is not energized, said solenoid energizing means being connected to said amplifier disabling means to render said disabling means ineffective to disable said amplifying means when said solenoid is energized, and means connected to said solenoid energizing means for controlling the energizing current delivered to said solenoid and delivering a relatively high initial surge of energizing current and a relatively low steady-state holding current to said solenoid.

2. In a dictating machine, means for amplifying electrical voice signals input to said machine, an indicator lamp, means for causing said lamp to burn with a relatively high initial intensity when said amplifying means supplies no output signal and, when on output signal is supplied by said amplifying means, to burn with an intensity lower than said initial intensity by an amount dependent upon the magnitude of said output signal, a solenoid-operated drive clutch, a switch adapted to connect the solenoid of said clutch to an electrical energization source, electrical circuit means connected to said switch for short-circuiting the input terminals of said amplifying means, for disabling said amplifying means and thereby causing said lamp to burn with said high initial intensity when said solenoid is not energized, and for presenting, when said solenoid is energized, an essentially open circuit across said amplifier input terminals and rendering said amplifying means effective to perform its amplification function, and means connected to said switch for controlling the energizing current delivered to said solenoid and delivering a relatively high initial surge of energizing current and a relatively low steady-state holding current to said solenoid.

3. In a dictating machine, means for amplifying electrical voice signals input to said machine, an indicator lamp, means for causing said lamp to burn with a relatively high initial intensity when said amplifying means supplies no output signal and, when an output signal is supplied by said amplifying means, to burn with an intensity lower than said initial intensity by an amount dependent upon the magnitude of said output signal, a solenoid-operated drive clutch, a switch adapted to connect the solenoid of said clutch to an electrical energization source, electrical circuit means connected to said switch for short-circui'ting the input terminals of said amplifying means, for disabling said amplifying means and thereby causing said lamp to burn with said high initial intensity when said solenoid is not energized, and for presenting, when said solenoid is energized, an essentially open circuit across said amplifier input terminals and rendering said amplifying means effective to perform its amplification function, and means connected to said switch for controlling the energizing current delivered to said solenoid and delivering a relatively high initial surge of energizing current and a relatively low steadystate holding current to said solenoid, said energizing current control means comprising a transistor, a steadystate current-limiting resistor connected in series with said solenoid and between the emitter and the collector electrodes of said transistor, said resistor having one terminal connected to one terminal of said electrical source, said switch being connected in series between the other terminal of said source and the series combination of said solenoid and said resistor, and a resistance-capacitance network connected to the base electrode of said transistor and adapted to develop an initial transistent signal input to said transistor when said switch is initially closed, said transient signal being adapted to render the emitterconductor path in said transistor highly conductive for the duration of said transient.

References Cited by the Examiner UNITED STATES PATENTS 3,056,606 10/62 Schnueler 179100.2 X 3,099,827 7/63 Wu 179-1001 IRVING L. SRAGOW, Primary Examiner.

BERNARD KONICK, Examiner.

Claims

1. IN A DICTATING MACHINE HAVING MEANS FOR AMPLIFYING ELECTRICAL VOICE SIGNALS INPUT TO SAID MACHINE, AN INDICATOR LAMP, MEANS FOR CAUSING SAID LAMP TO BURN WITH A RELATIVELY HIGH INITIAL INTENSITY WHEN SAID AMPLIFYING MEANS SUPPLIES NO OUTPUT SIGNAL, AND WHEN AN OUTPUT SIGNAL IS SUPPLIED BY SAID AMPLIFYING MEANS, TO BURN WITH AN INTENSITY LOWER THAN SAID INITIAL INTENSITY BY AN AMOUNT DEPENDENT UPON THE MAGNITUDE OF SAID OUTPUT SIGNAL, A SOLENOID-OPERATED DRIVE CLUTCH, AND MEANS FOR ENERGIZING THE SOLENOID OF SAID CLUTCH, THE IMPROVEMENT OF MEANS FOR DISABLING SAID AMPLIFYING MEANS AND THEREBY CAUSING SAID LAMP TO BURN WITH SAID HIGH INITIAL INTENSITY WHEN SAID SOLENOID IS NOT ENERGIZED, SID SOLENOID ENERGIZING MEANS BEING CONNECTED TO SAID AMPLIFIER DISABLING MEANS TO RENDER SAID DISABLING MEANS INEFFECTIVE TO DISABLE SAID AMPLIFYING MEANS WHEN SAID SOLENOID IS ENERGIZED, AND MEANS CONNECTED TO SAID SOLENOID ENERGIZING MEANS FOR CONTROLLING THE ENERGIZING CURRENT DELIVERED TO SAID SOLENOID AND DELIVERING A RELATIVELY HIGH INITIAL SURGE OF ENERGIZING CURRENT AND A RELATIVELY LOW STEADY-STATE HOLDING CURRENT TO SAID SOLENOID.