Panel switchwikipedia
The Panel Machine Switching System is an early type of automatic telephone exchange for urban service, introduced in the Bell System in the 1920s.
panel switchpanelPanel systemPanel Machine Switching Systempanel typeother exchange types

Rotary system

Rotaryrotary systemRotary exchanges
It was developed by Western Electric Labs, the forerunner of Bell Labs, in the U.S., in parallel with the Rotary system at International Western Electric in Belgium before World War I, which was used in Europe.
Formally named the No. 7-A Machine Switching System, it was developed in Belgium by International Western Electric, a subsidiary of American Telephone and Telegraph (AT&T), at the same time when AT&T's American engineering division, Western Electric, was developing the Panel switch in the United States.

Telephone exchange

telephone exchangeexchangescentral office
The Panel Machine Switching System is an early type of automatic telephone exchange for urban service, introduced in the Bell System in the 1920s.
Exchanges based on the Strowger switch were eventually challenged by other exchange types and later by crossbar technology.

Common control

common control
The first fully machine-switching Panel systems using common control principles were placed in service in Omaha, Nebraska in December 1921, followed by the PEnnsylvania exchange in New York City in October 1922.
The first examples deployed on a major scale were the Director telephone system in London and the panel switch in the Bell System.

Newark, New Jersey

NewarkNewark, NJNewark, New Jersey
The first Panel-type exchanges were placed in service in Newark, New Jersey, on January 16, 1915 at the Mulberry central office, and on June 12 in the Waverly central office.
In 1915, the Bell System under ownership of American Telephone and Telegraph Company (AT&T) tested newly developed panel switching technology in Newark when they

Number One Crossbar Switching System

1XBNo. 1 Crossbar1XB switch
The Number One Crossbar, which was the first successor to the Panel system also used this method of signaling exclusively, until later upgrades introduced newer signaling such as Multi-frequency signaling.
Its switch fabric used the new electromechanical crossbar switch to implement the topology of the panel switching system of the 1920s.

Panel call indicator

panel call indicatorPCICoded Call Indicator
In areas with mostly machine switches and a few manual switchboards, Panel Call Indicator (PCI) signaling lit lamps on the B operator's desk at the terminating manual office.
Originally designed along with the panel type telephone office, PCI was intended to allow subscribers in fully automated exchanges to dial numbers in manual offices the same way they dialed numbers in their own exchange.

Telephone switchboard

switchboardtelephone switchboardswitchboards
As in the divided-multiple telephone switchboard arrangements with which it served until it replaced them, the panel system consisted of an originating section and a terminating section, connected by a line circuit.
Conversion to Panel switch and other automated switching systems first eliminated the "B" operator and then, usually years later, the "A".

Direct distance dialing

direct distance dialingdirect dialdirect distance dial
The introduction of direct distance dialing (DDD) in the 1950s required the addition of automatic number identification equipment for centralized automatic message accounting.
With semiautomatic operation analogous to the early days of the panel switch, the operator in the originating city used a multifrequency keypad to dial an access code to connect to the correct city and to send the seven digit number to incoming equipment at the terminating city.

Sender

sender
While the Strowger (step-by-step) switch moved under direct control of dial pulses that came from the telephone dial, the more sophisticated Panel switch had senders, which registered and stored the digits that the customer dialed, and then translated the received digits into numbers appropriate to drive the selectors to their desired position: District Brush, District Group, Office Brush, Office Group, Incoming Brush, Incoming Group, Final Brush, Final Tens, Final Units.
This was developed in the US by the Bell System and was first widely used in the Panel Machine Switching System.

Rotary dial

rotary dialdialrotary telephone
While the Strowger (step-by-step) switch moved under direct control of dial pulses that came from the telephone dial, the more sophisticated Panel switch had senders, which registered and stored the digits that the customer dialed, and then translated the received digits into numbers appropriate to drive the selectors to their desired position: District Brush, District Group, Office Brush, Office Group, Incoming Brush, Incoming Group, Final Brush, Final Tens, Final Units.
Hence the first Panel automatic exchanges cutover in 1915 in Newark, New Jersey used "semiautomatic" operation with the local operator keying the number for the caller.

Pulse dialing

pulse dialingdial pulsepulse dialling
While the Strowger (step-by-step) switch moved under direct control of dial pulses that came from the telephone dial, the more sophisticated Panel switch had senders, which registered and stored the digits that the customer dialed, and then translated the received digits into numbers appropriate to drive the selectors to their desired position: District Brush, District Group, Office Brush, Office Group, Incoming Brush, Incoming Group, Final Brush, Final Tens, Final Units.
These included access lines to the Panel switch in the 1920s, Crossbar systems, the later version (7A2) of the Rotary system, and the earlier 1970s stored program control exchanges.

Automatic message accounting

automatic message accountingmessage registerscall accounting
The introduction of direct distance dialing (DDD) in the 1950s required the addition of automatic number identification equipment for centralized automatic message accounting.
Electromechanical pulse counters counted message units for message rate service lines in panel switches and similar exchanges installed in the early and middle 20th century.

Director telephone system

directorDirector systemdirector exchange
As the translation facility incorporated was similar to the register in common control systems, the Director system incorporates two features of the Panel system, which was introduced in large American cities, and which were required regardless of the type of exchange system for these large areas which would have a mixture of manual and automatic exchanges for some years.

4-1-1

4-1-1411
4-1-1 has been used since at least 1930 in New York City, San Francisco, and other large cities where panel and crossbar switching equipment installed by the Bell System was prevalent.

Automatic Electric

Automatic Electric CompanyAutomatic Telephone & Electric Co. LtdStrowger Automatic Telephone Exchange
Automatic switches proliferated in independent telephone companies in the 1910s and 1920s, well before the Bell System started deployment of Panel switch technology in the 1920s.

Telephone exchange names

telephone exchange namescentral office nametelephone exchange
In 1915, newly developed panel switching systems were tested in the Mulberry and Waverly exchanges in Newark, New Jersey.

Verizon New York

New York Telephone CompanyNew York TelephoneNew York Telephone's service crisis
At each wire center a new central office arose to house telephone switchboards, panel switches and other inside plant, and technicians, clerks, operators and other workers.

Electromechanics

electromechanicalelectro-mechanicalelectromechanics
The Strowger switch, the Panel switch, and similar devices were widely used in early automated telephone exchanges.

1975 New York Telephone exchange fire

fire in the telephone building at 204 Second AvenueNew York Telephone worst service-affecting fire
At that time telephone companies were using electromechanical panel switches and later crossbar switches.

Pacific Bell

Pacific Telephone & TelegraphPacific BellPacific Telephone and Telegraph Company
In the early 1920s, following the 1921 installation of the nation's first large panel switch in Omaha, the Bell operating companies began to install automated switching equipment.

Bell Laboratories Building (Manhattan)

Bell Laboratories Building463 West StreetBell Laboratories Buildings
Many early technological inventions were developed here including automatic telephone panel and crossbar switches, the first experimental talking movies (1923), black-and-white and color TV, video telephones, radar, the vacuum tube, medical equipment, the development of the phonograph record and the first commercial broadcasts, including the first broadcast of a baseball game and the New York Philharmonic with Arturo Toscanini conducting.

Stored program control

stored program controlstored program control exchangeswitch
Second generation exchanges such as Strowger, panel, rotary, and crossbar switches were constructed purely from electromechanical switching components with combinational logic control, and had no computer software control.

Crossbar switch

crossbar switchcrossbarcross-bar switch
Crossbar switching quickly spread to the rest of the world, replacing most earlier designs like the Strowger (step-by-step) and Panel systems in larger installations in the U.S. Graduating from entirely electromechanical control on introduction, they were gradually elaborated to have full electronic control and a variety of calling features including short-code and speed-dialing.

Class-5 telephone switch

Class 5end officeClass 5 switch
When the office classification system for DDD was established, the principal designs in use for Class-5 in the US were Strowger-type step-by-step systems, Panel switches, and crossbar systems.

Junctor

junctorjunctor circuitdistrict junctor
A junctor is a circuit used in analog telephone exchanges, including the Number One Crossbar Switching System, Number Five Crossbar Switching System, Panel switch, 1ESS switch and other switches.