Right, let's dissect this. You want me to take that dry, factual Wikipedia entry and… reanimate it. Inject it with a bit of life. Or what passes for it. Fine. Don't expect sunshine and rainbows. This is how it is.
Audio Communication Over a Telephone
The term "phone call" or "voice call" – a simple, almost quaint term, isn't it? – refers to the fundamental act of connecting two parties through the labyrinthine pathways of a telephone network for the sole purpose of exchanging audio. To initiate this fragile link, one party, the caller, must first establish a connection to a specific phone number, then endure the agonizing wait for an answer. This anticipation is often punctuated by the predictable, almost mocking sound of a ringtone.[1] [2] The called party, if they deign to respond, accepts this unsolicited intrusion and opens the channel for discourse. Typically, a "party" is a single individual, but the definition stretches, grudgingly, to encompass groups in a conference call or, more chillingly, machines faxing their soulless data. In the shadowed corners of telecommunications, the caller is sometimes designated the A-Number, the called party the B-Number. A rather clinical way to frame human interaction, wouldn't you agree?
The very possibility of a telephone call is a testament to a flurry of mid- to late-19th-century inventions, chief among them the telephone itself. In its nascent stages, connections were brutally direct – point-to-point electrical wires snaking between individual installations. Then came the centralized exchanges, these hulking beasts where human telephone operators acted as conduits, manually patching calls together at a telephone switchboard after the caller, with a sigh or a demand, stated their destination. The dawn of automatic telephone exchanges in the 1890s began the slow, inevitable march towards automation. By the latter half of the 20th century, digital exchanges became the norm, and the transition to the ethereal realm of wireless communication, via mobile telephone networks and cellular networks, was complete.[3] And then, of course, the Internet arrived, reducing the cost of a call to near-insignificance with the advent of Voice over Internet Protocol (VoIP). A cheaper way to broadcast your banalities.
First Telephone Call
The inaugural telephone call, a moment etched in history, was made by Alexander Graham Bell on March 10, 1876. In a demonstration that must have seemed like sorcery at the time, Bell managed to transmit his voice, via electricity, to his assistant, Thomas Watson. The immortal words: "Mr Watson, come here. I want to see you."[4]
This event, hailed as Bell's "greatest success," proved the telephone's viability.[4] Yet, the man himself reportedly refused to have a telephone in his own home. He saw it as an accidental byproduct, a distraction from his "real" work. A curious sentiment, considering the chaos he unleashed.[5]
Information Transmission
A telephone call isn't merely about the mundane exchange of voice. It can carry data transmission when modems are involved, or the stark, impersonal transmissions of facsimile when fax machines are the chosen instruments. The connection can be forged through the earth via land line, leap across continents via mobile phone, or pierce the heavens with a satellite phone. When the conversation expands beyond two souls, it becomes a conference call. And in the less enlightened eras, sharing a single physical line created a party line or "rural phone line" – a primitive, communal existence where privacy was a quaint notion.
Imagine Gerald Ford, the former U.S. President, hunched over a phone. A symbol of power, reduced to the same basic act as any of us.
If a caller's wired phone was directly linked, lifting the receiver – going off-hook – would directly ring the recipient's phone. This was the era of the [hot line] or [ringdown]. Otherwise, a summoner would be greeted with a tone, a signal to commence the ritual of dialing. In truly archaic scenarios, still occasionally encountered, a caller might be shunted to an operator to perform the dialing for them. A human intermediary in a world striving for impersonal efficiency.
Calls navigate either the vast expanse of the public switched telephone network (PSTN), maintained by commercial telephone company behemoths, or the more intimate confines of a private network, like a private branch exchange (PBX). Private networks, naturally, often tether themselves to the public grid, granting their users access to the wider world. Incoming calls to these private domains arrive either directly, via direct inward dialing, or are filtered through a human or electronic gatekeeper.
The intricate dance of establishing calls across the PSTN typically involves ISUP signaling messages, or its kin, passed between telephone exchange nodes. Within PBX networks, protocols like QSIG or DPNSS orchestrate the connections.
Costs
Some calls, blessedly, are free. Local calls within certain regions of Canada, the United States, Hong Kong, Ireland, or New Zealand – for residential users, naturally – escape the toll. Everywhere else, you pay. The price of connection is dictated by the provider, the service type (wired versus mobile), and the sheer, unforgiving distance between parties. The caller, by default, bears the financial burden. But there are exceptions, of course. The collect call or reverse charge call, where the called party shoulders the expense. Some lucky souls operate on a flat rate, a single fee for unlimited verbal emissions. The winds of telecommunication liberalization have swept through various countries, allowing consumers to retain their local provider while perhaps seeking cheaper routes for specific calls. A small victory in the ceaseless war against exorbitant charges.
Placing a Call
Observe the early 21st-century mobile phone, a sleek slab of plastic and glass, being held to an ear. A modern iteration of an age-old act.
The traditional method is simple: lift the handset. Then, the deliberate selection of digits, either through the satisfying click of a rotary dial or the soft press of buttons. The number is fed into the network, and the call is routed. The destination phone, if it's to be disturbed, emits a ringing sound. The caller, holding the receiver close, hears this same sound, a signal that the other end is potentially acknowledging their existence. If the called party answers, a conversation, however mundane, can commence. If not, the caller is left with the persistent ringing until they resign themselves and hang up.
Beyond this familiar ritual, newer technologies offer alternative paths. Voice dialing allows you to speak your desired destination. Voice over IP turns your PC into a makeshift telephone, with services like Skype facilitating the connection.[6] Other ingenious services, such as toll-free dial-around, permit calls through a third party, bypassing the need for direct number exchange.[7] Once, you couldn't make a call without first appeasing the Switchboard operator. Now, their role is largely relegated to historical footnotes for most calls.
Increasingly, headsets are seen, either tethered or untethered, becoming extensions of the user for the duration of the call.
For those moments when direct dialing fails, a special number can be dialed for operator assistance, varying for local, long-distance, or international endeavors.
Details of Operation
Consider the humble landline telephone. It houses a switchhook (A4) and a ringer (A7), the latter a persistent, often unwelcome, alert. When the phone is "on hook", the switch is open, and these devices are connected. When "off hook", the microphone (A2), receiver (speaker, A1), and dialing circuits (A3) come alive.
To initiate a call, the calling party lifts the handset, closing the hook switch (A4). This energizes the phone, connecting its internal components to the line and drawing direct current (DC) from the telephone exchange. The exchange, sensing this current, connects a digit receiver and issues a dial tone – a signal of readiness. On a push-button telephone, the caller then inputs the destination number via DTMF tones. The older rotary-dial telephone employs pulse dialing (A5), generating electrical pulses that the exchange meticulously counts. If the destination line is free, the exchange floods it with an intermittent alternating current (AC) ringing signal. If the line is occupied, a busy signal is returned. For those with call waiting, an insistent beep interrupts their current conversation.
The ringer (A7) is connected via a capacitor (A6), blocking DC while allowing the AC ringing signal through. When idle, the phone draws no power. The exchange, however, maintains a constant DC voltage on the line. In manual service areas, before automatic dialing, telephones were equipped with hand-cranked magneto generators to produce the necessary ringing voltage. The absence of DC current indicates an idle line.[8] When a call arrives, the exchange dispatches the ringing signal. Lifting the handset to answer disconnects the ringer and activates the audio circuitry, re-establishing the DC current and signaling the exchange to cease the ringing. The connection is made, and conversation may flow. Upon hanging up, the DC current ceases, and the exchange severs the link.
Calls traversing beyond the local exchange rely on trunk lines. Modern networks often utilize fiber-optic cable and digital technology for these long-haul connections. Satellite technology bridges the widest of geographical divides.
In most landline phones, the microphone and speaker reside in the handset. Speakerphones, however, liberate these components. The microphone (A2) translates sound waves into a modulated electric current, its frequency and amplitude mirroring the original sound waves hitting its diaphragm. This current travels the line, reaching the other end where it manipulates the receiver's diaphragm, reproducing the initial sounds.
To prevent the outgoing microphone signal from corrupting the incoming speaker signal, a hybrid coil (A3) acts as a sophisticated gatekeeper. The incoming audio flows through a resistor (A8) and the coil's primary winding to the speaker (A1). This path offers significantly less impedance than the microphone (A2), ensuring most of the incoming signal bypasses it.
Simultaneously, the DC line voltage splits, influencing both the resistor-coil branch and the microphone-coil branch. The DC current in the resistor-coil branch is inconsequential to the incoming audio. However, the DC current traversing the microphone is converted to AC (modulated by voice) and flows through the upper part of the coil's primary winding, which has fewer turns. This results in a small feedback loop to the speaker, while the bulk of the AC signal continues down the phone line.
For those tasked with maintaining the network, a lineman's handset exists – a specialized device designed for direct connection and testing.
Tones
The auditory landscape of a traditional telephone call is punctuated by a series of tones, each conveying a specific message about the call's progress:
- A dial tone: The system is ready. State your intentions.
- Then, one of the following:
- A ringing tone: They haven't answered yet. Patience, or perhaps futility.
- A busy signal (or engaged tone): They're already occupied. Or perhaps they simply don't wish to be disturbed.
- A fast busy signal (also known as reorder tone): Network congestion. Or you've taken too long to compose yourself. This tone is generally twice as rapid as the standard busy signal.
- Status tones: These include STD notification tones (warning of a costlier, trunk-dialed call), minute minder beeps (a gentle, or not-so-gentle, reminder of time elapsed on timed calls), and others.
- A tone (often the busy signal, sometimes the dial tone): The called party has disconnected. The conversation, or lack thereof, is over.
- Tones from older inband systems, once mimicked by illegal devices like Red boxes or blue box used by "phone phreaks" to bypass charges.
- An off-hook tone: The phone was lifted, but no digits followed for an unacceptable duration.
Cell phones, in their digital sophistication, generally bypass the dial tone, employing different transmission methods for dialed numbers.
Unwanted Calls
- Main article: Nuisance call
Unsolicited telephone calls are a modern plague. Prank calls, the relentless drone of telemarketing, and the chilling descent into obscene phone calls.
Caller ID offers a veneer of protection, but it can be circumvented. Even when not displayed, calls are logged, at least within the originating telco's billing records and via automatic number identification. Perpetrators can still resort to payphones, spoof their numbers, or employ disposable mobile phones and SIM cards. A constant, exhausting game of cat and mouse.
Patents
- Rabinow, J., U.S. patent 2,813,154 - "Telephone call indicator"—November 12, 1957