Programmable phonograph device

The present invention comprises an improvement in programmable phonograph record players which provide automatic sound track selection of the recorded portions of a record. The improvements comprise the provision of an optical scanner mounted on the tone arm including an incandescent light source for directing visible light onto the record surface and a photodetector for receiving light reflected by the record surface. In an alternate embodiment, a differential sensor system includes a light emitting diode and a pair of photodetectors for detecting the presence of a highly reflective, unrecorded land area between two successive recorded sound track portions of the record. In another embodiment, the scanner includes a pair of alternately illuminated light emitting diodes and a single photodetector for receiving the light energy, directed by the light emitting diodes onto the record surface, reflected toward the photodetector. An auxiliary tone arm lift and sweep mechanism is controlled by a digital logic system connected to the scanner to move the tone arm in a position to play a preselected number of sound track bands as dictated by a programmable memory.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention comprises an improvement in programmable phonograph 
record turntables and changers such as that shown and described in 
copending patent application Ser. No. 682,079 filed Apr. 30, 1976 and 
assigned to the assignee of the present invention and relates, in 
particular, to improvements in the record land detecting systems of such 
devices. 
2. Brief Description of the Prior Art 
Most musical recordings are sold in the form of disc-type photograph 
records where a plurality of sound track selections are spaced apart by 
unrecorded land areas which include an unrecorded groove to carry the 
stylus to the next sound track selection. Often a user of this type of 
phonograph record will want to hear fewer than all of the sound track 
selections on a particular record. Various record players have been 
proposed which are designed to permit a user to select a certain number of 
sound tracks to be played. The known prior art devices include U.S. Pat. 
Nos. 2,952,464 to Stimler, 3,368,080 to Nakagiri and 3,937,903 to Osann. 
It has been found that the amount of light which will be reflected by a 
particular unrecorded land area will vary greatly from record to record 
and even between proximate areas of the same sound track. Thus, there is a 
need for greater reliability in programmable phonograph devices and the 
present invention is directed toward such a device. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an improved sound track 
selector for permitting preprogrammed selection of any of several bands of 
a record. 
Another object of the invention is to provide an improved sensor system for 
detecting the presence of an unrecorded land area beneath the phonograph 
stylus. 
In accordance with the above and other objects, the present invention 
provides a simplified adaptive threshold land sensor including an 
incandescent light source in combination with a phototransistor. In an 
alternate embodiment, the sensor system comprises a differential or 
balanced system in which a pair of photodetectors are mounted on either 
side of the light source for comparing the reflectivity of the record 
surface between two points to indicate the presence of a land area. In 
another design, a pair of alternatingly pulsed light emitting diodes are 
mounted on either side of a single phototransistor to again measure the 
reflectivity between two positions on the record surface to locate the 
presence of a land area. The above embodiments are therefore capable of 
reliably indicating the presence of a particular unrecorded land area 
beneath the sound stylus regardless of condition or other physical 
characteristics of the record surface. 
Other objects, features and advantages of the invention will be apparent 
from the following detailed description taken in connection with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention is an improvement in programmable phonograph record 
turntables and changers such as that shown in copending patent application 
Ser. No. 682,079 filed Apr. 30, 1976, and assigned to the assignee of the 
present invention. That application discloses all of the mechanical and 
electronic elements of a programmable phonograph record changer and is 
incorporated herein by reference. Where appropriate, various references 
will be made to the specific reference numerals and elements of the above 
application. The present disclosure is to be considered an exemplification 
of the principles of the invention and is not intended to limit the 
invention to the embodiments illustrated. 
FIG. 2 is a front elevational view of the end of a phonograph tone arm, 
generally designated 11, similar to FIG. 8 of the above incorporated 
application, showing an optical scanner or sensor, generally designated 
13. The optical scanner includes a light source 15 in the form of a 
miniature incandescent lightbulb 15a having a generally tubular envelope 
or a light emitting diode 15b. Miniature bulbs of this type are commonly 
referred to as grain of wheat bulbs because of their obvious physical 
similarities. The bulb 15a is mounted at an angle of approximately 
71/2.degree. with the vertical and directs a beam of light 17 onto a 
typical record surface, generally designated 19. As shown in FIG. 2, the 
axial centerline of the light rays are impinging an unrecorded land area 
21 on the record surface between two adjacent recorded record sound track 
bands 23. The relative height of the end of the tone arm 11 with respect 
to the record surface 19 provides an illuminated "cue" spot on the record 
surface of approximately 0.05 inches in diameter. This spot provides a 
cuing light easily visible to the operator which illuminates the record 
surface in the area of the phonograph stylus. A portion of the light is 
reflected upwardly as shown by the line 25 to a phototransistor 27 mounted 
on the tone arm 11 with its axis approximately 71/2.degree. tilted from 
the vertical. Therefore, the angle between the emitted light 17 and the 
reflected light 25 will be approximately 15.degree.. Referring to FIG. 2, 
the sensor operates on the principle that the amount of light reflected 
from the record surface 19 will be substantially higher from an unrecorded 
land area than from a recorded sound track portion 23. As stated above, a 
light emitting diode 15b of the visible or infrared light generating type 
may be used in place of the bulb 15a and similarly supplied with direct 
current through appropriate limiting resistors. A 50 milliamp DC supply 
has been found to suffice in a typical instance to provide adequate output 
from an associated phototransistor such as 27 shown in FIG. 2. 
Referring to FIG. 1, the light source 15 (either the incandescent bulb 15a 
or the light emitting diode 15b) is shown connected to a DC supply 
voltage, V.sub.CC of approximately 15 volts which through resistors 31 and 
33 energizes the incandescent light source 15a at or below one-half candle 
power level. The light 17 generated by the light source 15 is reflected to 
the phototransistor 27 connected between the terminals of the same power 
supply. The resultant photo current develops a voltage on line 35 across 
the load resistor 37. Typically, this output voltage has been found to 
range between 3 and 7 volts for a particular light source and 
phototransistor set. This wide variation in the phototransistor output 
illustrates the fact that the surface reflectivity can be substantially 
different for different disc recordings. On a particular record surface, 
the reflectivity of the unrecorded land areas may range from approximately 
1.3 to 1.7 times the reflectivity of the recorded or grooved portion. 
Therefore, an adaptive threshold circuit, generally designated 41, of FIG. 
1 is designed to reliably indicate the presence of a land area below the 
phonograph stylus. The operating principles of an adaptive threshold 
circuit are described with reference to FIG. 10 in the above copending 
application. 
Referring to FIG. 1, the output of the phototransistor is applied to the 
non-inverting input of two feedback operational amplifier 43 and 45. The 
amplifiers 43 and 45 may typically be one of four operational amplifiers 
such as one-quarter of an LM324 standard quad op-amp. The gain of each 
amplifier, 43 and 45 is essentially a function of the ratio between the 
1500 ohm feedback resistors 47 and the ground return resistors. In the 
case of amplifier 43, a 1k resistor 49 is used and in the case of 
amplifier 45, a 500 ohm resistor 51 is used in combination with a variable 
1k resistor 53. The output of amplifier 43 is applied to an RC network 
including a 500k resistor 57 and a 10 micro-farad capacitor 59. The 
charging and discharging time constants of this network are identical and 
typically are of the order of 5 seconds. The output voltage on line 61 is 
the integral of the output of amplifier 43. Hence, the voltage on line 61 
provides a reference voltage which rises and falls slowly in harmony with 
the average reflectivity conditions of the record area approximately two 
to five grooves behind the instantaneous position of the playback 
transducer stylus. 
The output from amplifier 45 is applied to a similar RC network including a 
120k resistor 63 and a 1 micro-farad capacitor 65. The time constant of 
this network is substantially shorter, typically of approximately 0.1 
second. Hence, the output on line 67 through resistor 69 represents 
contemporaneous or real-time surface reflectivity conditions of the area 
near the stylus. Line 61 is connected to the non-inverting input of an 
operational amplifier 71 and line 67 is connected to the inverting 
terminal of amplifier 71. The operational amplifier thus operates as a 
comparator. 
Resistor 53 is adjusted to vary the gain of amplifier 45 so that its output 
is slightly lower than the output of amplifier 43 when the stylus is 
tracking a recorded or grooved portion of a record. In this case, since 
the non-inverting terminal of the comparator 71 is higher, the output of 
the comparator will be high, approximately V.sub.CC. The small amount of 
integration in time delay which results in the output 67 has the attribute 
of eliminating all extraneous, spurious and therefore undesirable short 
term reflections resulting from localized imperfections on the surface of 
the phonograph record. However, as the sensor 13 moves above a land area 
21, as shown in FIG. 2, the higher reflectivity of the land area 21 causes 
the voltage on 67 to exceed the voltage on 61. At this instant, when the 
voltage on 67 exceeds the voltage on 61, the comparator output switches 
from V.sub.CC to approximately ground or low, and remains low until such 
time as the voltage on 61 again exceeds the voltage on 67. This, of 
course, occurs after the scanner 13 moves past the land area 21 onto the 
next recorded surface 23. The output of the comparator 71 is applied to a 
signal stretcher, generally designated 73, as described in the copending 
application. The output of the signal stretcher 73 is applied to an 
inverter/comparator 75 as described in the above copending application. 
The output of the inverter/comparator 75 is the land area signal which is 
subsequently inverted by transistor Q.sub.3 and input to the logic system 
on line 77. The five volt output logic signal on line 77 is applied to the 
control means 38 or logic system shown in FIGS. 11 through 18 of the above 
incorporated application. Thus, the adaptive threshold circuit shown and 
described with reference to FIG. 1 provides a reliable output which 
indicates the presence of a land area below the phonograph stylus. 
FIG. 9 shows diagrammatically how the adaptive thresholding is 
accomplished. The chart plots the voltage on lines 61 and 67 as well as 
the output of the comparator 71. As can be seen, during the initial period 
when traversing a sound track portion, the voltage on 61 is higher than 
that on 67, the output of the comparator 71 is high, or V.sub.CC. However, 
as soon as the voltage on 67 exceeds the voltage on 61 when encountering a 
land area, the comparator 71 switches states and goes low until 67 is 
again lower than 61. The chart also shows that the long integration time 
provides a smooth curve on line 61 while the shorter integration time 
constant provides a more fluctuating voltage on line 67. In particular, 
the undulations shown on line 67 are the result of record warpage and are 
generally of the order of one or two cycles per disc rotation. 
As described in the above referenced application, the phonograph tone arm 
traverses the record surface 19 are a much higher speed when in its sweep 
or traverse mode, compared to its tracking or playback mode, and therefore 
it is necessary to change the time constants of the respective RC networks 
when the phonograph is in its traverse or sweeping mode. In the sweep of 
traverse mode, a 100k resistor 81 is connected in parallel with the 
resistor 57 and a 15k resistor 83 is connected in parallel with the 
resistor 63 to accomplish the necessary time constant changes for the 
respective RC networks. Similarly, a 47k resistor 85 is connected in 
parallel with the 300k resistor of the signal stretcher 73. These parallel 
connections are effected in the circuit by three switches. The switches 
are designated SWA, SWB and SWC. Typically, the switches are implemented 
through the use of CMOS PNP/NPN semiconductor switches such as the 
currently available CD4066 quad CMOS switch 89 shown in FIG. 1. The 
switches, SWA, SWB and SWC, are made when a logic level signal of 
approximately V.sub.CC is connected to line 91 shown connected to pins 13, 
5 and 6 of the quad switch 89. This signal is supplied by the solenoid 
driver circuits, as shown in FIG. 10 of the previous application, when the 
tone arm lift and traverse solenoids 112 and 122 therein are actuated. 
Thus, the reduction of the time constants of the RC integrator networks 
permits the adaptive threshold circuit 41 to operate in a much faster mode 
and still reliably detect the occurrence of a land area below the playback 
transducer stylus. 
FIG. 8 is a chart constructed by measuring the output voltage across a load 
resistor 99A or 99B generated by a phototransistor 101A or 101B receiving 
reflected light from a light emitting diode 103A or an incandescent light 
source 103B, respectively. The chart shows portions of three different 
bands on a particular record, one being constructed in phantom, the other 
solid, and the other represented by a dash line. From the chart, it can be 
seen that the reflectivity of a record surface varies greatly even when 
the sensor is traversing a recorded or grooved portion of the record 
surface. The uppermost or highest voltage levels on the chart just to the 
right of the center of the chart represent the presence of a land area 
below the sensor and it can be seen that even the reflectivity of the 
unrecorded land area also is variable for a particular land area. This 
chart shows than an adaptive threshold circuit will be much superior to a 
circuit having a fixed threshold since the latter could not reliably 
indicate the presence of a land area. 
In another embodiment, shown in FIGS. 3, 4 and 5, a differential or 
balanced system, generally designated 111 (FIG. 3), is shown. Referring to 
FIGS. 4 and 5, the end of the tone arm is modified to include a scanner 
generally designated 113 including an inner phototransistor 115, an outer 
phototransistor 117 and a single light emitting diode 119 between the 
phototransistors and on centerline with the phonograph stylus 121. The 
other mechanical elements of the tone arm head, and tone arm lift and 
traverse mechanism, are identical to those described in the above 
copending application. As shown in FIG. 5, the sensor 113 provides a 
differential reading as the tone arm moves across the record surface. 
Particularly, referring to FIG. 5, the inner or leading phototransistor 
115 is shown as receiving light from the light emitting diode 119 which 
has been reflected from an unrecorded, intraband land area 21 while the 
phototransistor 117 is receiving light from a recorded or grooved portion 
23 of the record surface. Thus, in this embodiment, the occurrence or 
presence of a land area will be indicated by a rapid increase in the 
output of the phototransistor 115 when compared to the output of the 
phototransistor 117. When both are receiving light reflected by the 
grooved portion 23, there is substantially no difference between their 
respective outputs. 
Referring to FIG. 3, the light emitting diode 119 is shown to provide 
reflected light to both phototransistors as represented by the arrows 125. 
The light emitting diode is driven from a pair of 24 ohm resistors in 
parallel connected to a 555 oscillator 127. The oscillator 127 provides a 
rectangular wave form output for pulsing the light emitting diode 119 with 
a duty cycle of approximately 15%. The light from the pulsed light 
emitting diode 119 is reflected to the two phototransistors 115 and 117 
which have been matched so as to provide the same output for the same 
amount of received light energy. Typical light emitting diodes are 
identified as Fairchild Semiconductor E04 components. In the schematic, 
the upper phototransistor 117 represents the outer phototransistor while 
the lower phototransistor 115 represents the inner phototransistor with 
respect to their positions on the end of the tone arm in relation to the 
outer edge of the phonograph record. The light received by the inner 
phototransistor 115 provides a voltage on line 131 generated across the 1k 
load resistor 133. The outer phototransistor 117 provides a voltage on 
line 135 generated across a 1k resistor 139. As described previously, the 
output of the two phototransistors will be approximately equal when the 
light being received is reflected from the same type of record surface, 
i.e., sound track portion or land area portion, so that subtracting the 
one from the other will cancel the two components. However, upon arrival 
of the land area reflection to the inner phototransistor, there is a large 
change in output of phototransistor 115 which results in a readily 
recognizable differential between the two signals. 
The output of phototransistor 117 is applied to a non-inverting amplifier 
141, again one of four present in an LM324 quad op-amp. Line 135 is 
connected by a 50k resistor 143 to pin 5, the non-inverting side of the 
amplifier 141. Feedback is applied from the output pin 7 through a 120k 
resistor 145 to the inverting input, pin 6 of the amplifier 141. Pin 6 is 
connected to a 100k resistor 149 to ground. Therefore, the output from the 
amplifier on line 151 is approximately two times that supplied by the 
phototransistor 117. Line 151 is connected through a 100k resistor 153 to 
the inverting input, pin 9, of a second amplifier 154. The non-inverting 
input terminal, pin 10, of the amplifier 154 is connected through a 50k 
resistor 157 to line 131, the output of the inside phototransistor 115. In 
this manner, a difference signal is taken between the two phototransistor 
outputs. The output at pin 8 is the difference between the input at pin 10 
minus the input at pin 9. Typically, the output of amplifier 154 will be 
approximately 160 millivolts when the stylus is in the down position and 
approximately 170 millivolts when the stylus is in the up position. The 
output of amplifier 154 on line 159 is applied to the noninverting input 
pin 12 of a linear amplifier 161. The amplifier 161 includes feedback 
capacitor 163 connected in parallel with a 75k feedback resistor 165 and a 
variable 500k resistor 167. The resistor 167 is adjusted so that the 
overall gain of the amplifier 161 is between 20 and 30. Capacitor 163 
serves to roll off high frequency noise disturbances. An output on line 
169 of amplifier 161 exists only when there is an unbalanced signal 
between the phototransistor 115 and 117, when the inner phototransistor 
115 is receiving light reflected by a land area. Normally, when the two 
phototransistors 115 and 117 are receiving light reflected from a recorded 
portion, the output of amplifier 161 is approximately at ground. 
Therefore, a diode 171 conneced to line 169 disconnects the remainder of 
the circuit when the two phototransistors 115 and 117 are balanced. When 
an unbalanced signal is applied, the output on line 169 rises towards 5 
volts, or V.sub.CC, and charges a one micro-farad capacitor 173. This 
positive voltage is applied to the inverting side, pin 2, of a fourth 
operational amplifier 175. Again, the amplifier 175 is connected as a 
comparator with the non-inverting input, pin 3, connected to the junction 
between a 330k resistor 177 and a 390k resistor 179. Therefore, 
approximately 21/2 volts are applied to pin 3 and when the input at pin 2 
goes above 2.5 volts, the threshold of the comparator 175, the output at 
pin 1, switches from 3.8 volts to ground. 
In passing over a land area, since the light emitting diode 119 is being 
pulsed, the output of the comparator will develop more than one and 
perhaps three or four apparent land area commands. This signal is 
inadequate to drive the logic portion as previously described. Another 555 
timer 183 is connected to pin 1 by line 181 so that it will start timing 
only after the comparator has returned to 3.8 volts. The length of time 
during which the timer 183 will output one pulse, a hig level pulse on 
line 185 is determined by the 47k resistor 187 and the series connected 
25k resistor 189. These two resistors in conjunction with a 10 micro-farad 
capacitor 191 determine the length of time during which the timer 183 will 
be high once it has been triggered by the output comparator. Pin 3 is 
connected by line 185 to the logic system, as described in the above 
referenced application, to indicate that a land area has been encountered. 
Again, as described above, when the stylus is in its up position so that 
the tone arm is sweeping across the record, the circuit may be adjusted 
slightly since the sensor is moving across the record surface at a much 
faster rate. To adjust the circuit, a transistor 192 is connected between 
a 330k resistor 193 and ground. The base of transistor 192 is connected by 
a line 195 to the solenoid control circuitry as described in the previous 
applicaton to a point, the collector of Q.sub.4, so as to provide 
approximately 10 volts to the base of the transistor 192 when the logic 
system provides a lift command to move the stylus to the up position. When 
this voltage occurs, transistor 192 saturates so that its collector drops 
essentially to ground thereby connecting the 330k resistor to ground. The 
time constant of the original combination including the one micro-farad 
capacitor 173 and the one megohm resistor 197 is therefore shortened by a 
factor of approximately 3 to 1 which is sufficient to accommodate the more 
rapid variations in the signal because of the faster tone arm traverse 
movement. Thus, the differential system 111 provides an alternate method 
of detecting land areas on a record surface by comparing the reflectivity 
of the record surface immediately prior to the stylus with that 
immediately following the stylus on its movement inwardly across a record 
surface. 
An alternate type of differential system is shown in block diagram in FIG. 
6. In this alternate embodiment, a pair of light emitting diodes D.sub.1 
and D.sub.2 are mounted on either side of a single phototransistor 199 in 
a similar manner as shown in FIG. 4 above. In this embodiment, the light 
emitting diodes D.sub.1 and D.sub.2 are alternatively pulsed to provide 
reflected light from the record surface to the phototransistor 199. 
Referring to the block diagram of FIG. 6, an oscillator 201 provides a 
square wave output 203 as shown in the top of FIG. 7. This output is 
connected to a divide by two flip-flop 205 providing an output Q and a 
second output Q. The Q and Q signals are shown in a time relationship with 
one another and the square wave 203 in in the bottom of FIG. 7. In this 
case, the Q signal saturates a transistor 207 connected between D.sub.1 
and ground to illuminate D.sub.1 when the signal is high. Likewise, the Q 
signal is connected to a second transistor 209 which saturates to 
illuminate D.sub.2 when Q is high. The light emitting diodes alternately 
illuminate the phototransistor 199 as represented by arrows 211 and 213. 
The output voltage developed across a load resistor 215 is applied to two 
parallel circuits. 
Referring to the right of FIG. 6, the voltage developed across resistor 215 
as a result of a light pulse from light emitting diode D.sub.1 is passed 
by field effect transistor 217, turned on by logic signal Q. As a result, 
the output of the phototransistor 199 is applied to a capacitor 219. This 
field effect transistor 217 and capacitor 219 forms a sample-and-hold 
circuit. Likewise, a second field effect transistor 221 in the lower 
circuit has its gate connectedto Q so as to provide a second 
sample-and-hold circuit, charging capacitor 223 to the output of the 
phototransistor 199 when Q is high. The DC outputs of the respective 
circuits are then compared to one another as above described with referece 
to FIG. 3 to provide a reliable land sensor. Again, this system is 
insensitive to absolute amplitude reflections and does not require matched 
phototransistors as described above. The output of the light emitting 
diodes D.sub.1 and D.sub.2 can easily be adjusted and balanced by adusting 
resistors 227 and 229. 
The three above systems, the land sensor system using a DC light source, 
and the two differential systems are designed for use with a programmable 
phonograph record changer such as that described in the incorporated 
patent application. All of the mechanical elements therein as well as the 
logic circuitry and the tone arm lift and sweep circuitry is shown in said 
copending application and need not be described again herein. 
Additionally, the 555 timer as shown in FIG. 3 could be incorporated in 
the DC illuminator circuit of FIG. 1 as well as in the parent application 
without departing from the present invention. 
The foregoing detailed description has been given for clearness of 
understanding only and no unnecessary limitations are to be understood 
therefrom as some modificatons will be obvious to those skilled in the art 
.