RECORD CHANGER SIZE SENSING

How record changers sense the record size

Many record changers can automatically sense the size of the record it is playing. Here is a list of the different methods used, and how each one determines the kinds of stacks of records it can play.

 
GROUP METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
N
O
 
S
E
N
S
O
R
Size Switch The user selects the size of the record by moving a control. Two, three, or four sizes. Only one size allowed in the stack.

Plays single record on turntable.

Sample is
Dual 1209

3-size knob on the right

Dual 1209
Speed and Size Switch The user selects the size and the speed of the record by moving one control. Usually some speed-size combinations are not available.

This unit allows 7" 33, 10" 33, 12" 33, 7" 45, & 12" 78.

Two or three sizes. Only one size allowed in the stack.

Plays single record on turntable.

Sample is
Garrard SL-72B

speed-size knob on the left

Garrard SL-72B
Record Shelf Position The user selects the size of the records by setting the side shelf to fit the records. Two or three sizes. Only one size allowed in the stack.

Plays single record on turntable.

Sample is
Philco M-22

turn shelf on the left

Philco M-22
Spindle Selected Size The user selects the size of the record by changing spindles. Each diameter and hole size has a different spindle. The spindles slope different amounts, and the lower ends of the spindles are different lengths, to select the arm setdown point. Two or three sizes. Only one size allowed in the stack.

Plays single record on turntable.

Sample is
Milwaukee-Erwood 11600

change spindle to change size

Milwaukee-Erwood 11600
 
GROUP METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
T
U
R
N
T
A
B
L
E
 
S
E
N
S
O
R
Rising Feelers The first record on the turntable is sensed repeatedly for the entire stack. Sensors mounted in the turntable or beside it detect the first record. The record depresses the sensors according to its size. Three sizes. Only one size allowed in the stack.****

Plays single record on turntable.

Sample is
PE-2040

pins in turntable and near rim

PE 2040
Swinging Feeler Swinging feeler moves in to touch the edge of the first record on turntable.

Must have small turntable.

Three sizes. Only one size allowed in the stack.

Plays single record on turntable.

Sample is
Philips AG 1116

feeler in curved slot

Philips AG 1116
Hole Size Feeler A rising feeler rises 1/2" from the center of the record. If it touches a record, it plays 12" 33.
If it does not touch a record, it plays 7" 45.

A slot in the 45 spindle lets the feeler pass through it.

Plays only 12" 33 and 7" 45.

Two sizes. Only one size allowed in the stack. ****

Plays single record on turntable.

Sample is
Magnavox Micro-Mini W712

feeler in turntable near center

Magnavox W712
3-Size Turntable Arm Scan The pickup arm moves down, and then inward to touch the edge of the first record on turntable. If it does not find a record, 7" operation is selected. Then the arm rises, moves inward, and sets down on the record.

Must have small turntable.

Three sizes. Only one size allowed in the stack.

Plays single record on turntable.

Sample is
Philips (unknown model)

protrusion on pickup arm

Philips AG 1116
 
GROUP METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
D
R
O
P
 
S
E
N
S
O
R
Droplever The falling record pushes the feeler down different amounts, or does not strike the feeler, selecting different record sizes. Two or three sizes can be intermixed in any order in the stack.

No single record on turntable.

Sample is
Collaro Continental RC-54

feeler protruding from slot

Collaro Continental
Tilting Feeler The feeler, shaped like the number 4, tilts forward before the record drops. Then the falling record strikes the sloped edge and pushes the feeler back different amounts, or does not strike the feeler, selecting different record sizes. Two or three sizes can be intermixed in any order in the stack.***

No single record on turntable.

Sample is
Glaser-Steers 77

feeler is behind overarm

Glaser-Steers 77
Semaphore The feeler axle is vertical. The falling record rotates the feeler away from the spindle different amounts, or does not strike the feeler, selecting different record sizes. Three sizes can be intermixed in any order in the stack.***

No single record on turntable.

Sample is
Garrard AT-60

curved object left of overarm

Garrard AT-60
 
GROUP METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
S
T
A
C
K
 
S
E
N
S
O
R
Index Arm The index arm touches the edge of the stack before the record drops, then backs off so the record can drop. If no record is found, automatic shutoff occurs. Three sizes. Larger records must be below smaller records.

No single record on turntable.

Sample is
Webster 100

arm left of overarm

Webster 100
3-Size Arm Scan The pickup arm head touches the edge of the stack before the record drops, then backs off so the record can drop. If no record is found, automatic shutoff occurs. Three sizes. Larger records must be below smaller records.

No single record on turntable.

Sample is
Collaro PH1252

protrusion on pickup arm

Collaro PH1252
Pickup Arm Scan The pickup arm touches the edge of the stack before the record drops, then backs off so the record can drop. If no record is found, automatic shutoff occurs. The use of a slipclutch allows odd-sized records to be played.

The photo shows the sensing action.

12" to 6". Larger records must be below smaller records.

No single record on turntable.

Sample is
Collaro Conquest TSC-640

protrusion on pickup arm

Collaro Conquest
 
GROUP METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
S
E
P
A
R
A
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R
E
C
O
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D
 
S
E
N
S
O
R
Pickup Arm Scan on Lowered Record The record lowers about half an inch. Then the pickup arm touches the separated record. It then backs off so the record can lower to the turntable. If no record is found, automatic shutoff occurs. A slipclutch allows odd-sized records to be played. This unit also lowers records slowly to the turntable. 12" to 6" can be intermixed in any order in the stack.

No single record on turntable.

Sample is
V-M 1555

protrusion on pickup arm

VM 1555
Pickup Arm Scan on Separated Record The record carrier moves the record over the turntable. Then the pickup arm touches the separated record. The record then drops to the turntable. If no record is found, automatic shutoff occurs. A slipclutch allows odd-sized records to be played. This unit keeps the unplayed and played records on separate shelves on the left. 12" to 6" can be intermixed in any order in the stack.

No single record on turntable.

Sample is
Thorens TD-224

protrusion on pickup arm

Thorens TD-224
Feeler Wheels After the record drops, feeler wheels lower from the bottom of the arm. The arm then moves in and sets the wheels down near the center of the record. Next, the wheels roll the arm toward the edge of the record. The wheels are canted and vertically aligned to make the arm stop at the edge of the top record on the turntable. Then the wheels retract and the arm plays the record. 12" to 6" can be intermixed in any order in the stack.

Plays single record on turntable.

Sample is
Dual 1006

feeler wheels in pickup arm (lower photo)

Dual 1006 Dual 1006 feeler
METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
Record Underside 3-Size Scan The arm moves toward the center of the turntable, and then rises to touch the stack. A smooth feeling surface is on top of the arm with a feeling edge. The pickup arm swings back and forth like a pendulum, moving farther out each time. The feeling stops if the feeler touches the edge of the bottom record of the stack. The pickup arm then pushes the record off the spindle ledge. Then the arm moves to play the record. Automatic shutoff occurs if the overarm is down, leaving the arm at the center of the record. 3 sizes can be intermixed in any order in the stack.

No single record on turntable.

Sample is
Triotrack 457

feeling surface on top of pickup arm (lower photo)

Triotrack 457 Triotrack 457 push
Record Underside Scan The arm moves toward the center of the turntable, and then rises to touch the stack. There are two special wheels on top of the arm and a feeling edge. The pickup arm oscillates like a pendulum, moving farther out each time. The feeling stops if the feeler touches the edge of the bottom record of the stack. The arm swings out and the record drops. Then the arm moves to play the record. If no record is found, automatic shutoff occurs. A slipclutch allows playing odd-sized records. 12" to 6" can be intermixed in any order in the stack.

No single record on turntable.

Sample is
Miracord PW 9

bar with wheels on top of pickup arm

Miracord 9 Miracord 9 feeling
Shelf Bottom Record Sensor The record shelf senses the size of the record while determining which pusher edge to use to push it off. 12" & 10" can be intermixed in any order in the stack.

No single record on turntable.

Sample is
Webster 70

feeler is inside side shelf

Webster 70
 
GROUP METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
C
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B
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A
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M
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H
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D
S
Size Switch and Tilting Feeler The user selects the size range of the records by moving a control. A falling record feeler allows some intermix of record sizes. Usually 12" & 10" intermixed, with 7" played separately. Some mix 12" with the selected size.

No single record on turntable.

Sample is
Collaro Sentinel RC-53

slide switch on right, sensor by overarm base

Collaro Sentinel
Speed-Size Switch and Droplever The user selects the size range of the records by moving the speed control. A falling record feeler allows some intermix of record sizes.

The sample unit does 12" & 10" 78, 12" & 10" 33, 7" 33, 7" 45.

Usually 12" & 10" intermixed, with 7" played separately. Some mix 12" with the selected size.

No single record on turntable.

Sample is
V-M 406

small knob, sensor on rear of tonearm

V-M 406
Rising Feeler and Tilting Feeler The rising feeler (white arrow) determines whether a stack of 7" records, or larger records, is being played. A falling record feeler (black arrow) allows intermix of 12" & 10" records. Usually 12" & 10" intermixed, with 7" played separately.

No single record on turntable.

Sample is
V-M 935

feelers at white and black arrows

V-M 935
METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
Droplever and Size Override Control The falling record feeler allows intermix of record sizes. The size override control allows play of a single record. Three sizes intermixed in any order.

Plays single record on turntable.

Sample is
Philips AG1003

left pushbutton, feeler protruding from slot.

Philips AG1003
C
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B
I
N
A
T
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O
N
 
O
F
 
M
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T
H
O
D
S
Rising & Tilting Feeler
and Overarm Position
The rising feeler determines whether a stack of 7" records, or larger records, is being played. A falling record feeler allows intermix of 12" & 10" records.

Raising the overarm and placing it so the tip is over the rim of the record repeats that size record. The overarm is shown in the 10" position.

12" & 10" intermixed, with 7" played separately.

No single record on turntable.

Sample is
RCA RP-215 R (modified)

feelers at same places as white and black arrows on VM unit above

RCA RP-215 R
Tilting Feeler and
Overarm Position
The feeler, shaped like the number 4, is under the record. The falling record strikes the sloped edge, pushing the feeler back different amounts, or misses the feeler, selecting different record sizes.

When raised, the overarm can be placed into one of three positions for repeating the three record sizes.

Two or three sizes can be intermixed in any order in the stack.***

Plays single record on turntable.

Sample is
Glaser-Steers 3000

feeler is behind overarm

Glaser-Steers 3000
METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
Semaphore and
Overarm Position
The feeler axle is vertical. The falling record rotates the feeler away from the spindle different amounts, or does not strike the feeler, selecting different record sizes.

A special clip can hold the overarm raised in one of three positions for repeating the three record sizes.

Three sizes can be intermixed in any order in the stack.***

Plays single record on turntable.

Sample is
Garrard AT-60 with the clip

curved object left of overarm

Garrard AT-60
Semaphore and Swinging Feeler The feeler axle is vertical. The feeler moves toward the spindle when the cycle begins, and retracts after the arm sets down. 7" records miss the feeler.

The single-play spindle raises the swinging feeler so its roller can contact a single record on the turntable.

The multiple-play spindle lowers the swinging feeler below the turntable, so falling records of various sizes turn the semaphore different amounts.

Three sizes can be intermixed in any order in the stack.

Plays single record on turntable.

Sample is
Dual 1008

curved objects left of arm base

Dual 1008
C
O
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B
I
N
A
T
I
O
N
 
O
F
 
M
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D
S
3-Size Arm Scan and Size Override Control The pickup arm touches the stack before the record drops, then backs off so the record can drop. If no record weight is on the spindle, automatic shutoff prevents the scan. The size override control sets the size for a single record on the turntable. Three sizes. Larger records must be below smaller records.

Plays single record on turntable.

Sample is
Miracord PW-161

protrusion on pickup arm, knob in group

Miracord PW-161
METHOD HOW IT WORKS RECORD ORDER REQUIRED SAMPLE CHANGER PHOTO
Semaphore and Index Arm The combined feeler axle is vertical. The feeler moves toward the spindle at the beginning of the cycle, contacting the largest record on the spindle. A falling 12" record rotates the semaphore away from the spindle, selecting 12" operation. 10" and 7" records do not push the feeler out enough to select a different size. If the feeler does not contact a record, automatic shutoff occurs. 12" & 10" intermixed in any order, 7" must be last.***

No single record on turntable.

Sample is
Garrard RC 210

curved object over the tonearm

Garrard RC 210
Pickup Arm Scan and Index Arm The pickup arm touches the edge of the stack before the record drops, then backs off so the record can drop. If no record is found, automatic shutoff occurs. The use of a slipclutch allows odd-sized records to be played.

The index arm performs the same feeling action at the same time, but is used for automatic speed change. It allows small 45 RPM records to be stacked above larger 33 RPM records.

12" to 6". Larger records must be below smaller records.

No single record on turntable.

Sample is
Collaro Conquest TSC-640 Custom

protrusion on pickup arm, index arm on left behind overarm (brass)

(Silver arm is a record cleaner)

Collaro Conquest Custom
 

*** This sensor has also been used to intermix record speeds in the stack (large 33 RPM with small 45).

**** This sensor has also been used to sense the record speed for the stack (large 33 RPM or small 45).

repeating discs

In the following discussion, the use of Audiotex record repeating discs is listed. The repeating discs are 2.75 inches (7 cm) in diameter, with the standard 1.5 inch hole used for large-hole records. A spider adaptor can be inserted to make the repeating discs work with small-hole records. Two repeating discs are shown at right:

When making up a record stack, place a repeating disc on top of the record that is to be played twice. When the repeating disc drops, the changer will play the record under it again, if it can.

Note that they can not be used with the following kinds of changers:

  1. Changers that have the active record dropping parts in the side shelf. Repeat discs in the stack can cause the changer to break records.
  2. Changers with the nodding spindle dropping mechanism (Philco). Repeat discs in the stack can break records.
  3. Changers that change records by methods other than dropping or lowering them down a spindle (e.g. Thorens TD-224).
  4. Changers that measure the size of the record while it is separated from the other records.
  5. Changers that can't drop the discs (some need enough weight in the record to work the spindle).

Changers that feel the unplayed stack require that another record the same size as the record to be repeated must be placed above the repeat disc.

The following is a table of properties of these methods. The column "REPEAT DISCS" tells how the repeating discs can or can not be used with each type or record changer.

PROPERTIES OF SIZE SENSING METHODS
 
GROUP METHOD SIZE INTERMIX SINGLE RECORD PLAY REPEATING RECORDS REPEAT DISCS
NO
SENSOR
Size
Switch
none Yes Yes* Yes**
Speed and
Size Switch
none Yes Yes* Yes**
Record Shelf
Position
none Yes Yes* Center push Yes**
Shelf push No
Spindle
Selected Size
none Yes Yes* DANGER - breaks records

METHOD SIZE INTERMIX SINGLE RECORD PLAY REPEATING RECORDS REPEAT DISCS
TURNTABLE
SENSOR
Rising
Feelers
none Yes Yes* Yes**
Swinging
Feeler
none Yes Yes* Yes**
Hole Size
Feeler
none Yes Yes* Yes**
3-Size Turntable
Arm Scan
none Yes Yes* Yes**

METHOD SIZE INTERMIX SINGLE RECORD PLAY REPEATING RECORDS REPEAT DISCS
DROP
SENSOR
Droplever
 
2 or 3 sizes, random order Only smallest size Only smallest size* Only smallest size**
Tilting
Feeler
2 or 3 sizes, random order Only smallest size Only smallest size* Only smallest size**
Semaphore
 
2 or 3 sizes, random order Only smallest size† Only smallest size* Only smallest size**

METHOD SIZE INTERMIX SINGLE RECORD PLAY REPEATING RECORDS REPEAT DISCS
STACK
SENSOR
Index
Arm
2 or 3 sizes, larger records must be below smaller records no no If next record
is same size**
3-Size
Arm Scan
3 sizes, larger records must be below smaller records no no If next record
is same size**
Pickup
Arm Scan
12" to 6", Larger records must be below smaller records no no If next record
is same size**

METHOD SIZE INTERMIX SINGLE RECORD PLAY REPEATING RECORDS REPEAT DISCS
SEPARATE
RECORD
SENSOR
Pickup Arm Scan
on Lowered Record
12" to 6", random order no no no - shuts off**
or wrong size
Pickup Arm Scan
on Separated Record
12" to 6", random order no no no - shuts off
Feeler
Wheels
12" to 6", random order Yes Yes* Yes**
Record Underside
3-Size Scan
3 Sizes, random order no no If next record
is same size**
Record
Underside Scan
12" to 6", random order no no If next record
is same size**
Shelf Bottom
Record Sensor
2 sizes, random order no no DANGER - breaks records

METHOD SIZE INTERMIX SINGLE RECORD PLAY REPEATING RECORDS REPEAT DISCS
COMBINED
METHODS
Size Switch and
Tilting Feeler
12" & 10", random order 10" & 7" 10" & 7" * 10" & 7" **
Speed-Size Switch
and Droplever
12" & 10", random order 10" & 7" 10" & 7" * 10" & 7" **
Rising Feeler and
Tilting Feeler
12" & 10", random order 10" & 7" 10" & 7" * 10" & 7" **
Droplever and
Size Override Control
3 sizes, random order Yes If override control used* Size set on override control**
Rising & Tilting Feelers
and Overarm Position
12" & 10", random order Yes If overarm position used* 10" & 7" **
Tilting Feeler and
Overarm Position
3 sizes, random order Yes If overarm position used* Only 7" records**
Semaphore and
Overarm Position
3 sizes, random order Yes If overarm position used* Only 7" records**
Semaphore and
Swinging Feeler
3 sizes, random order Yes Only 7" records* Only 7" records**
3-Size Arm Scan and
Size Override Control
3 sizes, Larger records must be below smaller records Yes If override control used* If next record
is same size**
Semaphore and
Index Arm
12" & 10" random order, 7" last No No 10" & 7" **
Pickup Arm scan
and Index Arm
12" to 6", Larger records must be below smaller records, 33 below 45 no no If next record
is same size**
 

NOTES:

* Provided that the record dropping and/or auto shutoff mechanisms can be persuaded to repeat records.

** Provided that the record dropping mechanism is capable of dropping the disc.

Do not use repeat discs with a record dropping mechanism that pushes the rim of the record. It could break the record on top of the disc.

The exact range of sizes provided depends on the design of the individual model.

COMPANIES USING SIZE SENSING METHODS
 
GROUP METHOD COMPANIES
NO
SENSOR
Size
Switch
Many, including Admiral, BSR, Collaro, Dual, GE, Glenburn, Maestro, Magnavox, Miracord, Panasonic, Philips, RCA, Seeburg, Technics, VM, Zenith
Speed and
Size Switch
Admiral, BIC, BSR, Dual, Garrard, Miracord, PE, Philips, RCA, Technics, VM
Record Shelf
Position
Many, including Admiral, Aero, Belmont, Bendix, Emerson, Markel, Milwaukee-Erwood, Motorola, Philco, Philips, RCA, Seeburg, Webster, VM, Zenith
Spindle
Selected Size
Milwaukee-Erwood

METHOD COMPANIES
TURNTABLE
SENSOR
Rising
Feelers
Admiral, PE, Philco, Philips
Swinging
Feeler
Capehart, Philips
Hole Size
Feeler
Magnavox, Philips
3-Size Turntable
Arm Scan
Philips

METHOD COMPANIES
DROP
SENSOR
Droplever
 
BSR, Collaro, Crescent, Lesa, Panasonic, Philips, RCA, Silvertone, Supraphon, Universal Camera
Tilting
Feeler
Balfour, Collaro, Farnsworth, GE, Glaser-Steers, Philips, Silvertone, VM, Webster, Zenith
Semaphore
 
Garrard, PE, Silvertone, Webster

METHOD COMPANIES
STACK
SENSOR
Index
Arm
Garrard, Webster, Zenith
3-Size
Arm Scan
Collaro, Magnavox, Miracord, Philips
Pickup
Arm Scan
BSR, Collaro, Magnavox, Triotrack

METHOD COMPANIES
SEPARATE
RECORD
SENSOR
Pickup Arm Scan
on Lowered Record
PE, VM
Pickup Arm Scan
on Separated Record
Lincoln, Thorens
Feeler
Wheels
Dual, Luxor
Record Underside
3-Size Scan
Triotrack
Record
Underside Scan
Miracord
Shelf Bottom
Record Sensor
Aga, B&O, Dual, Garrard, Philips, Thorens, Webster

METHOD COMPANIES
COMBINED
METHODS
Size Switch and
Tilting Feeler
Collaro, Philips, Thorens
Speed-Size Switch
and Droplever
Miracord, Webster, VM
Rising Feeler and
Tilting Feeler
Admiral, BSR, RCA, Telefunken, VM
Droplever and
Size Override Control
Philips, Supraphon
Rising & Tilting Feeler
and Overarm Position
Modified RCA
Tilting Feeler and
Overarm Position
Glaser Steers
Semaphore and
Overarm Position
Modified Garrard
Semaphore and
Swinging Feeler
Dual
3-Size Arm Scan and
Size Override Control
Miracord
Semaphore and
Index Arm
Garrard, Wumo
Pickup Arm scan
and Index Arm
Modified Collaro
 

NOTES ON THE LETTERS IN MODEL NUMBERS:

The letters in various model numbers usually mean "record changer" in various languages.