The group that wrote this paper, after presenting their ideas to the class. From the left the Patent Examiner?, Alex Hey, J. Kirby Robinson, and Scott Stroud.

United States Patent Office

Application for Letters Patent

R. Alex Hey, J. Kirby Robinson, Scott B. Stroud of Charlottesville, VA

Improvements in Electrical Transmission of Sound

February 16, 1995

Abstract

Improving upon Alexander Graham Bell's photophone patent, the proposed design claims a mechanism for transmitting sound waves through variation in intensity of light rays. In response to sound sent through a cylindrical mouthpiece, a diaphragm stretched over the opposite end of the mouthpiece vibrates. This undulation alters the flow of current between two closely spaced metal contacts, one of which is attached to the taut diaphragm. When touching, the two contacts complete a circuit containing a light and power source. The intensity of the light depends upon and fluctuates with the amount of current supplied to the light source. These variable emissions from the light are received by a means for transforming solar energy to electrical current. The means for transforming has analog output based on the variable intensity of the light. This output can be sent to a generic receiver. We claim the mechanism as described by these components.

United States Patent Office

Application for Letters Patent

R Alex Hey, J. Kirby Robinson, Scott B. Stroud of Charlottesville, VA

Improvements in Electrical Transmission of Sound

February 16, 1995

To all whom it may concern:

We, R Alex Hay, J. Kirby Robinson, and Scott B. Stroud of Charlottesville, Virginia, have invented new and useful improvements in the means of transmission in the field of telephony, of which the following document will specify.

Prior art in this field includes designs by Alexander Graham Bell described in patents 174,465, 186,787, and, most importantly, his photophone patent, as well as designs held by the Smithsonian Institution. The communications devices described in the aforementioned documents operate upon the principle of using air vibrations to produce an undulating current in a transmission device, this current being sent to a receiver, whereupon it is translated into its previous state. The device which most relates to our design, the photophone, uses light as a means for the conversion of these vibrations into electrical energy.

Our design is based on the same principles and goals but uses an improved means for accomplishing the task. Where in previous designs vibrations caused variations in the direction of reflected light rays, our design uses a switched circuit to cause variations in the intensity of the light rays. This provides much better accuracy in the conversion of these variations to a transmittable signal.

The system of transmission which we have designed uses the sound and air waves induced by speaking into a mouthpiece, consisting of a cylinder of rigid material open at both ends, a membrane, which is stretched across one end of the cylinder, and two metal contacts. The sound waves through the cylinder cause vibrations in the membrane on which is located one of the electrical contacts. The second contact, which is secured to the mouthpiece by a support, is suspended over the first contact in such a way as to allow only the slightest of contact between the two. Air and sound waves from speech into the cylinder cause slight variations in the distance between the two contacts, thereby varying the amount of electrical current which continues in a circuit to which the two contacts are connected.

The two contacts act as a switch in the circuit which also includes a power source and a light source located within an opaque container. The power source provides the current to the circuit, and as this current is carried by the motion of the first contact against the second, the intensity of the light produced by the light source changes proportionally to the signal created by the vibrations on the membrane. The light from the light source is incident upon a device capable of converting light into energy. When fluctuations in this light occur, the current provided by the conversion device will vary in proportion to the fluctuations of the light. When the conversion device is connected in a circuit with a receiver, the analog variations in the current from the device act as a signal which can be converted back into the original sounds uttered into the mouthpiece.

The following is a detailed description of the figures accompanying this document. First we will describe the mouthpiece, and then we shall describe how the mouthpiece interconnects with the remainder of the phone.

Figure 1 is a model of the mouthpiece. The mouthpiece consists of a rigid cylinder (A) open at both ends. A flexible membrane (B) is stretched over one end of the open cylinder. There are two metal contacts involved. The first(C) is attached directly the membrane, and the second(D) is suspended over the first with a support (E). Each of the contacts is connected to the same circuit (F) which has a current flowing though it, such that the contacts act as a switch in this circuit. The contacts are calibrated so that they are only slightly touching. The slightest vibrations of the membrane will cause the intermittent opening and closing of the switch. When the membrane is caused to vibrate by oscillations of air in the cylinder, the contacts are made to intermittently switch the circuit from open to closed in a manner proportional to the pattern of vibrations. When these vibrations are caused by speech, the vibrations of the contacts send a signal which represents the speech pattern spoken into the mouthpiece.

Figure 2 is a model of the five main parts of the system we have designed. The design idea originated from the Smithsonian photophone design, but we have preserved only the idea of using light as the transmission medium. Electricity from the power source (G) Vows through the circuit (H), which remains closed during standby operation of the telephone transmitter. Vibrations in the mouthpiece (I) then cause variations in the current flowing through the circuit as described in the previous paragraph. A light source (J) is also connected to the circuit, and when the current in the circuit fluctuates, this causes the intensity of the light from the light source to vary in proportionality. The light source is enclosed in a light-proof box (K), along with a means for converting light into energy(L). Light from the light source is incident upon the conversion means. When the intensity of the light varies, the conversion means produces an analog signal in response to the varying light. This signal can then be transmitted.

Having described the specification for the new telephone design, and our desire for Letters Patent, we submit the following as our claim:

We claim the following:

1. A mechanism for translating sounds into fluctuating current, Comprising:

• a membrane stretched over one open end of a cylindrical mouthpiece, the other end open for voice transmission, wherein the membrane will vibrate in response to sound waves;
• two metal contacts, the first attached to the vibrating membrane surface, and the second suspended in close proximity to the first, wherein the contacts touch intermittently in response to vibrations of the membrane:
• a power source, to provide electricity to the light source:
• a light source, activated through completion of the circuit by the touching of the first and second metal contacts;
• a circuit consisting of the following previously mentioned elements, in series order: the two metal contacts the power source the light source
• a means for converting the intermittent light from the circuit to fluctuating electrical output for e ( use in transmitting to a separate receiver a signal corresponding to the vibrations of the membrane

whereby vocal sounds cause changes in current through said circuit thereby causing the light source to vary in intensity; these analog variations in light intensity are received by the means for transforming and converted to fluctuating output current.

This document used with permission of its authors.