The AT&T (also Lucent, now Avaya) Merlin telephone system was introduced in late 1983, branded American Bell Merlin. After the breakup of AT&T in 1984, it was rebranded AT&T Merlin. It was designed at the beginning of the 1980s prior to the Bell System Divestiture as a modern electronic replacement for the dated electromechanical 1A2 Key System. Earlier Bell attempts at an electronic key system, such as the Horizon and Dimension, were not as successful as were the much larger systems, in fact the Dimension was a PBX. The Merlin was the first small electronic system, replacing the Com Key 416. The Merlin system was originally sold in two-line, six-telephone (206); four-line, 10-telephone (410); and eight-line, 20-telephone (820) configurations. Later, there was a further 10-line, 30-telephone configuration, with an expansion KSU allowing the system to accommodate up to 70 telephones available (1030 and 3070 respectively).
AT&T Merlin Wikipedia
The 1A2 Key Telephone System and later ComKey series (4-16, 7-18, 14-34) had the following problems which the Merlin System sought to solve:Complex electromechanical line switches in every telephone
Each individual line pair plus control and light pairs must be run to each individual telephone, making for expensive on-premises wiring
Telephones were connected to one another using labor intensive point to point wiring
Control units consisted of many separate components including a power supply, line and feature module carrier, and punch blocks
Compared to more modern designs emerging in the 70's, manufacturing and maintaining the system became very expensive, especially by the 1980s
Basic features were present such as line switching, intercom, and hold but there was little possibility for addition of modern features
The Merlin System fixed these problems by:Having line switching done completely electronically at the Control Unit (Horizon was the first to do so)
Using 4-pair wiring (two digital switching, one for analog and one for intercom). The Horizon system was also the first "skinny cable" key system in the world and was introduced in the late 70's and like control unit switching provided the foundation of the system employed on Merlin
An important advance in handset design was the use of printed circuit boards and automated assembly which were economical to produce. Horizon, Dimension and Merlin were leaders in the use of PCB based handsets.
Fully electronic, all inclusive, one piece control unit
Slots for feature modules made possible optional extra price features such as Speed Dialing, Automatic Line Selection, and Redial
The Merlin telephones were also backwards compatible to the higher end enterprise systems, such as then System 75 and System 85 systems, then later Definity system, now called Communication Manager platforms.
The original Merlin was replaced with the Merlin Plus system in the late 1980s, using circuit cards to be expandable to 8 lines and 20 telephones, much like the original 820 model. The original Merlin Plus was dubbed the 820d. It was identical in features to the earlier Merlin 820 with the Feature Package 2 cartridge installed. Following the 820d was the 820d2. The 820d2 included the previous features as the 820d but featured an Automatic System Access (ASA) processor coupled with a voice synthesis capabilities and a Busy Buster. The ASA processor provided users with call forwarding, direct extension dial, and system answer capabilities. The busy buster allowed users to have the 820d2 automatically retry a busy number every minute for up to 10 minutes and notify the user when the call was connected. Both the ASA and Busy Buster required a their own voice terminal port to function. In the early 1990s, the Merlin II and Merlin Legend debuted with even more features and expandability, and new MLX telephones, but the system was also backwards compatible with the original Merlin telephones.
In 1999, Lucent Technologies introduced the Merlin Magix as the replacement for the Merlin Legend. The Magix's carrier was metal and, as such, modules were not encased inside plastic shells as they were with the Legend. The Merlin Magix supported new 4400 series digital telephones as well as older MLX telephones, but it did not support the old ATL series telephones. One important item with the conversion of Legend to Magix, is how MLX telephones used 2-pair wiring and the newer Magix/4400 series phones only used a single (1) pair. This made the Magix easier to install and more competitive in the marketplace, as most other digital PBX systems only used a single (1) pair to each station/telephone.
Due to declining sales and the introduction of the IP Office product line, Avaya retired the Magix on April 1, 2006.
Despite being over two decades old, the Merlin's modern electronic features and legendary Bell System era quality and durability still make the Classic Merlins very popular telephone systems with small businesses. Merlin sets shared over 50 pieces of plastic with digital telephones of the Dimension PBX as well as membrane switch technology (a first use in AT&T), reducing product introduction costs in 1983.
Feature Package 1 (Available for use in Classic Merlin 206, 410 only):5-party conference calling
Prevents outgoing calls on individual phones
Automatic outside and intercom dialing
Last number redial, automatic line selection, do not disturb
On hook dialing, call transfer, hold reminder, group listening
Feature Package II (Included same features as Feature Package I plus the following)Personal and system wide 3 digit speed dialing
Group paging zones
Music On HoldAllows a music source to be connected to the KSU which is heard by a caller on hold
Music On Hold/PagingAllows a music source to be connected to the KSU which is heard by a caller on hold
Provides a paging system connection and music on hold to be used as background music while no pages are being made.
Power Failure/Extra AlertProvides two RJ-11 jacks for standard touch-tone or rotary phone use in case of power failure.
Extra Alert jack for external notification device.