Manual Switching System: Story Of Old Times
Although the technology has been on its peak these days, the history of its development brings chills. When I was a kid, I loved to listen the stories my grandparents would tell me. They usually talked about how difficult it was to connect to a person living in a distant place. The tales of 1900s’ letters and telegram were very fascinating. But have you ever wondered what made the connection between people living in different places possible during that time?
There’s a term in telecommunication called switching system. The connection between caller and receiver is setup in this switching system. As a matter of fact, switches are used for connecting nodes in a network. But the switching we are talking about is switching speech signals. The system where a collection of these switching elements is used to set a common path between two ends is switching system.
At Present, we use automatic switching systems but when our grandparents were of our age, they had manual switching system. Microphones, in early years, used batteries to get energized as to send speech signals. These batteries were categorized as:
· Local battery exchange
· Central battery exchange
Manual switching system uses terms such as calling subscriber, receiving subscriber and operator. In both the exchanges, when one subscriber calls another, operator is the one who connects them.
Local battery exchange includes magneto which had to be rotated in calling subscriber’s end. This helps in charging the battery to establish the connection. A slip falls out in operator’s end to gain the attention of operator. Later, he/she makes a connection between both the subscribers.
Whereas, in central battery exchange, we don’t have magneto. It includes a handset and off-hook switch for this purpose. When the calling subscriber lifts the handset, off hook switch is closed, letting the current flow through circuit. This activates relay which allows the lamp to glow as to gain the attention from the operator.
These days, when we call someone and if due to some reasons it could not connect, we receive a voice, telling us why the call can’t be made. But since we are talking about manual switching system, the operator had to explain and use the instructions to tell calling subscriber about what’s going on.
There were certain signaling tones used for the same.
1. Dial tone: To ask the calling subscriber about whom to call.
2. Call in progress tone: To let the subscriber know that call has been made.
3. Ringing tone: To tell the subscriber that call is being connected.
4. Number unobtainable tone: to let the subscriber know that the called subscriber is not obtainable due to various reasons.
It is a time taking, complicated and vast process. Whereas automatic switching system processes all this within a fraction of seconds enabling us speedy and simple communication.
So, folks! Aren’t we lucky to live in this era? Phew! They saved us this lockdown.
