Community hub
Recent from talks
Knowledge base stats:
Talk channels stats:
Members stats:
Number One Electronic Switching System
The Number One Electronic Switching System (1ESS) was the first large-scale stored program control (SPC) telephone exchange or electronic switching system in the Bell System. It was manufactured by Western Electric and first placed into service in Succasunna, New Jersey, in May 1965. The switching fabric was composed of a reed relay matrix controlled by wire spring relays which in turn were controlled by a central processing unit (CPU).
The 1AESS central office switch was a plug compatible, higher capacity upgrade from 1ESS with a faster 1A processor that incorporated the existing instruction set for programming compatibility, and used smaller remreed switches, fewer relays, and featured disk storage. It was in service from 1976 to 2017.
The voice switching fabric plan was similar to that of the earlier 5XB switch in being bidirectional and in using the call-back principle.[clarification needed][citation needed] The largest full-access matrix switches (the 12A line grids had partial access) in the system, however, were 8x8 rather than 10x10 or 20x16. Thus they required eight stages rather than four to achieve large enough junctor groups in a large office. Crosspoints being more expensive in the new system but switches cheaper, system cost was minimized with fewer crosspoints organized into more switches. The fabric was divided into Line Networks and Trunk Networks of four stages, and partially folded to allow connecting line-to-line or trunk-to-trunk without exceeding eight stages of switching.
The traditional implementation of a nonblocking minimal spanning switch able to connect input customers to output customers simultaneously—with the connections initiated in any order—the connection matrix scaled on . This being impractical, statistical theory is used to design hardware that can connect most of the calls, and block others when traffic exceeds the design capacity. These blocking switches are the most common in modern telephone exchanges. They are generally implemented as smaller switch fabrics in cascade. In many, a randomizer is used to select the start of a path through the multistage fabric so that the statistical properties predicted by the theory can be gained. In addition, if the control system is able to rearrange the routing of existing connections on the arrival of a new connection, a full non-blocking matrix requires fewer switch points.
Each four stage Line Network (LN) or Trunk Network (TN) was divided into Junctor Switch Frames (JSF) and either Line Switch Frames (LSF) in the case of a Line Network, or Trunk Switch Frames (TSF) in the case of a Trunk Network. Links were designated A, B, C, and J for Junctor. A Links were internal to the LSF or TSF; B Links connected LSF or TSF to JSF, C were internal to JSF, and J links or Junctors connected to another net in the exchange.
All JSFs had a unity concentration ratio, that is the number of B links within the network equalled the number of junctors to other networks. Most LSFs had a 4:1 Line Concentration Ratio (LCR); that is the lines were four times as numerous as the B links. In some urban areas 2:1 LSF were used. The B links were often multipled to make a higher LCR, such as 3:1 or (especially in suburban 1ESS) 5:1. Line Networks always had 1024 Junctors, arranged in 16 grids that each switched 64 junctors to 64 B links. Four grids were grouped for control purposes in each of four LJFs.
TSF had a unity concentration, but a TN could have more TSFs than JSFs. Thus their B links were usually multipled to make a Trunk Concentration Ratio (TCR) of 1.25:1 or 1.5:1, the latter being especially common in 1A offices. TSFs and JSFs were identical except for their position in the fabric and the presence of a ninth test access level or no-test level in the JSF. Each JSF or TSF was divided into 4 two-stage grids.
Early TNs had four JSF, for a total of 16 grids, 1024 J links and the same number of B links, with four B links from each Trunk Junctor grid to each Trunk Switch grid. Starting in the mid-1970s, larger offices had their B links wired differently, with only two B links from each Trunk Junctor Grid to each Trunk Switch Grid. This allowed a larger TN, with 8 JSF containing 32 grids, connecting 2048 junctors and 2048 B links. Thus the junctor groups could be larger and more efficient. These TN had eight TSF, giving the TN a unity trunk concentration ratio.
Hub AI
Number One Electronic Switching System AI simulator
(@Number One Electronic Switching System_simulator)
Number One Electronic Switching System
The Number One Electronic Switching System (1ESS) was the first large-scale stored program control (SPC) telephone exchange or electronic switching system in the Bell System. It was manufactured by Western Electric and first placed into service in Succasunna, New Jersey, in May 1965. The switching fabric was composed of a reed relay matrix controlled by wire spring relays which in turn were controlled by a central processing unit (CPU).
The 1AESS central office switch was a plug compatible, higher capacity upgrade from 1ESS with a faster 1A processor that incorporated the existing instruction set for programming compatibility, and used smaller remreed switches, fewer relays, and featured disk storage. It was in service from 1976 to 2017.
The voice switching fabric plan was similar to that of the earlier 5XB switch in being bidirectional and in using the call-back principle.[clarification needed][citation needed] The largest full-access matrix switches (the 12A line grids had partial access) in the system, however, were 8x8 rather than 10x10 or 20x16. Thus they required eight stages rather than four to achieve large enough junctor groups in a large office. Crosspoints being more expensive in the new system but switches cheaper, system cost was minimized with fewer crosspoints organized into more switches. The fabric was divided into Line Networks and Trunk Networks of four stages, and partially folded to allow connecting line-to-line or trunk-to-trunk without exceeding eight stages of switching.
The traditional implementation of a nonblocking minimal spanning switch able to connect input customers to output customers simultaneously—with the connections initiated in any order—the connection matrix scaled on . This being impractical, statistical theory is used to design hardware that can connect most of the calls, and block others when traffic exceeds the design capacity. These blocking switches are the most common in modern telephone exchanges. They are generally implemented as smaller switch fabrics in cascade. In many, a randomizer is used to select the start of a path through the multistage fabric so that the statistical properties predicted by the theory can be gained. In addition, if the control system is able to rearrange the routing of existing connections on the arrival of a new connection, a full non-blocking matrix requires fewer switch points.
Each four stage Line Network (LN) or Trunk Network (TN) was divided into Junctor Switch Frames (JSF) and either Line Switch Frames (LSF) in the case of a Line Network, or Trunk Switch Frames (TSF) in the case of a Trunk Network. Links were designated A, B, C, and J for Junctor. A Links were internal to the LSF or TSF; B Links connected LSF or TSF to JSF, C were internal to JSF, and J links or Junctors connected to another net in the exchange.
All JSFs had a unity concentration ratio, that is the number of B links within the network equalled the number of junctors to other networks. Most LSFs had a 4:1 Line Concentration Ratio (LCR); that is the lines were four times as numerous as the B links. In some urban areas 2:1 LSF were used. The B links were often multipled to make a higher LCR, such as 3:1 or (especially in suburban 1ESS) 5:1. Line Networks always had 1024 Junctors, arranged in 16 grids that each switched 64 junctors to 64 B links. Four grids were grouped for control purposes in each of four LJFs.
TSF had a unity concentration, but a TN could have more TSFs than JSFs. Thus their B links were usually multipled to make a Trunk Concentration Ratio (TCR) of 1.25:1 or 1.5:1, the latter being especially common in 1A offices. TSFs and JSFs were identical except for their position in the fabric and the presence of a ninth test access level or no-test level in the JSF. Each JSF or TSF was divided into 4 two-stage grids.
Early TNs had four JSF, for a total of 16 grids, 1024 J links and the same number of B links, with four B links from each Trunk Junctor grid to each Trunk Switch grid. Starting in the mid-1970s, larger offices had their B links wired differently, with only two B links from each Trunk Junctor Grid to each Trunk Switch Grid. This allowed a larger TN, with 8 JSF containing 32 grids, connecting 2048 junctors and 2048 B links. Thus the junctor groups could be larger and more efficient. These TN had eight TSF, giving the TN a unity trunk concentration ratio.