The Evolution of the Softswitch
August 15, 2013
By Rachel Ramsey
, TMCnet Web Editor
Although your VoIP system can dictate how successful your business communications are, it wouldn’t be as strong without a quality softswitch behind it. Softswitches route calls and are usually used to control connections at a junction point between circuit and packet networks. To keep up with the transformation of telecommunications, the softswitch has gone through a lot of changes over the last few years.
The photo below answers the question, “Why do we need softswitches?”
The timeline below does not do the history of telecommunications justice; there is so much more that went into how we got to where we are today. But hopefully it gives you a little perspective and makes you think the next time you go to use your smartphone. With some help from our senior editor and telecom veteran Peter Bernstein, here is a general overview and approximate timeline of how the softswitch has evolved.
Switchboard Operators (1878 – 1960s)
After Alexander Graham Bell made his contribution to society with the telephone, switchboard operators were responsible for routing calls. They were the advanced technology of the time and enabled communication over phones. Switchboard operators were mostly women and they would have to connect calls by plugging callers’ phone lines into the phone lines of the people they wanted to talk to. Over the next 60 years, switchboard operators became one of the fastest-growing professions, until the 1950s, when developments in new technology made the move from manual to all electronic.
Image via Atomic Toasters
Strowger Switch (Step-by-Step, SXS) (1891-1938)
Invented by Almon Brown Strowger, this was the first example of an electromechanical stepping switch telephone exchange system, also known as a step-by-step (SXS) switch. Allegedly, Strowger invented the switch to level the playing field in his chose profession. He was an undertaker, and one local operator was the wife of a competing undertaker. Whenever someone would call and ask to be put through to Stowger, calls were deliberately put to his competitor. So, he decided to take matters into his own hands and help transform telecommunications.
The Strowger switch was the first effective implementation of automatic switching. Strowger formed “Strowger Automatic Telephony Exchange” in 1891, and the company exists today as AG Communications Systems (News - Alert).
Crossbar Switch (1938 – 1955)
The crossbar switch connects multiple inputs to outputs in a matrix manner – it’s essentially a relay mechanism consisting of ten horizontal paths and ten or 20 vertical paths, depending on what size switch is needed. Any horizontal path can be connected to any vertical path by means of magnets, and the points of connection are known as cross-points. Crossbar systems differ from Strowger systems in that they are designed using the common control concept, which sets up calls one a time, identifying a free path through link-trunked switches.
Electromechanical Switching (1955 – 1970s)
The Strowger switch, crossbar switch and Panel switch were early uses of electromechanical switches. An electromechanical switch opens and closes with an electromagnet – power is applied to the coil or magnet, which opens or closes mechanical contact points, pre-wired in a configuration suited best for the application.
Stored Program Control Analog (1965-1990s)
Stored program control (SPC) is the technical term for telephone exchanges controlled by a computer program stored in the memory of the system. Electromechanical switches had no software control. The biggest thing about SPC is that is enabled more sophisticated calling features. There are basically two types of SPC: centralized, where all the control equipment is replaced by a single processor that has to be able to handle 10 to 100 calls per second, and distributed, which is more available and reliable than centralized SPC and includes vertical and horizontal decomposition.
Digital Switching (1976 – present)
The digital era replaced everything with 1’s and 0’s. A digital switch handles digital signals generated at or passed through a telephone company’s ESS and then forwards them across the company’s backbone network. It receives digital signals that have been converted from users’ analog signals and switches them over with other incoming signals out to the WAN. Digital switches connect two or more digital circuits based on a dialed telephone number or other instruction.
VoIP Softswitch (1998 – present)
The proliferation of IP communications, particularly VoIP, among organizations and consumer has led us to the softswitch today. VoIP softswitches are split into Class 4 and Class 5 softswitches. Class 4 softswitches are mainly used to route large numbers of long-distance VoIP calls and for transit VoIP traffic between carriers, and Class 5 softswitches are used for both local and long-distance calls but are intended to work with end-users – they offer services such as IP PBX (News - Alert) features, call center services, calling card platforms and types of authorization. We’re seeing the transformation from softswitches to media gateway controller (MGC) in IP multimedia subsystems (IMSs), which are architectural frameworks for delivering IP multimedia services.
Edited by Rich Steeves