Client-Cashier talking device

In a number of life situations, for example, when a client and a cashier communicate at a railway station, in a bank, at a gas station, etc., they are assisted by an intercom. Indeed, in these cases it is unlikely to be able to talk without such a technical mediator. In addition, in production or in the office, there is always a need for remote communication between the director and the secretary, the head and subordinates, which is also provided by similar devices called overseas intercoms or interphones.

Intercom system: general description

The first thing that should be noted is the assignment of all the negotiation devices of the class in question to wired communication devices. Microphones and speakers on either side of the dividing talking wall are connected by electric wires. Even if such a device is called "wireless" (abroad, the English term "wireless" is used), this is a very conventional name, since for the transmission of an audio signal, the wires of the 220 V power supply are used.

If the voice message is played by a stationary speaker, then such a speakerphone is usually called an intercom. In the presence of subscribers instead of the usual telephone handsets there is an interphone.

A typical intercom is a simplex device, i.e., subscribers can not talk simultaneously. Interphones are always duplex intercoms, just like a regular telephone.

Both types of devices can be either single (for two subscribers) or multichannel.

The latter can be built either by a radial scheme with one central and multiple subscriber consoles, or by a "common bus" scheme with an arbitrary number of subscriber consoles of the same level.

Two-wire intercom communication lines and interphones

When from the beginning of the 70s of the last century industrial production of equipment for wired office communication systems began, it required the development of a single standard, a description of the electrical and logical properties of the communication channel included in any intercom device for compatibility of equipment from different manufacturers.

Soon appeared such a standard described a three-wire connected line in which two wires transmit the actual audio signal, and the third wire is the "plus" power line (the common wire is one of the sound wires). This line of communication played the role of a "common bus", to which all peer-to-peer subscribers were connected, that is, the speaker at the moment heard everything. Unofficially, this type of organization of the intercom was called party line, which means "shared line".

However, the name "two wire" (TW) was better adopted. It is due to the fact that in a three-wire line, only two wires are used directly for audio transmission. It should be emphasized that the term "line line" does not define the applicable communication standard, but only designates the principle of its organization - "everything with everyone". But any two-wire intercom could work only on this principle. As a result, it became associated only with them, although the party line can be organized using any (for example, four-wire) communication standard.

Modern modifications of TW-lines of intercoms and interphones

Despite the considerable age, two-wire (more precisely, three-wire) communication lines continue to be widely used in modern devices. As a rule, they occur in three modifications.

So, the well-known manufacturer Clear Com uses in its equipment a line with one common wire for power and audio, one signal wire and one power wire.

The second modification, used by Audiocom, includes a pair of audio cables, each of which is fed power, and a common wire.

And, finally, the third modification - with one common power wire, one wire for the first signal and power and a wire for the other signal.

Four-wire communication lines

In some modern intercoms and interphones for the organization of noise-protected duplex communication, the received and transmitted audio signals are galvanically isolated from each other, i.e., in the communication line there are two separate signal wires and two common wires. In such a four-channel line, power is transmitted through the signal wires. In this case, the power supplies of modern devices are characterized by a very low level of interference (their own) created by them.

Components of intercoms and interphones

These include power supplies, central consoles (for multi-channel intercoms with radial organization), subscriber sets (consoles, calling panels), connecting cables, etc.

A DC power supply is usually centralized. However, some subscriber units (especially remote ones for a considerable distance) can have their own power supplies. Many intercoms are connected to the mains, but there are devices powered by two or three 9-volt batteries connected in series.

Subscriber kits are mainly produced in three versions:

- with a microphone;

- in the form of a calling panel "speaker-microphone";

- with a combination of headset and speaker;

- in the form of a telephone receiver.

Their construction can also be represented by wall or desktop versions. Usually, subscriber sets are equipped with a button (switch) to turn on the microphone (with the "Transfer" button), sometimes combined with the "Call" light indicator, and the volume control of the phones (in the version with the headset). The subscriber set in the form of a calling panel (the "speaker-microphone" option) usually does not contain control elements.

Client-Cashier talking device

To provide communication between the client and the employee of the enterprise (manager, cashier, administrator), a special type of communicators "client-cashier" was created, since they are most widely used in cash desks of banks, cultural objects, avia-, auto- and railway stations. Such loudspeaker intercoms occupy an intermediate position between intercoms and interphones, since they are usually duplex, but may be able to be switched to a simplex communication mode on the part of the cashier. This is necessary, for example, so that he can consult his management about the problems of the client, without giving this conversation to his side. At the same time, the client can be heard at the box office.

Features of voice transmission in devices "client-cashier"

The cashier's workplace is usually reliably soundproofed from the premises where customers are located. Therefore, for such devices it is important to transmit the client's speech with maximum filtering of extraneous noise.

Manufacturers specifically reduce the spectrum of the transmitted signal to a frequency band from 100 Hz to 8.2 (sometimes 9.5) kHz, into which any human voice is known to fall. Sounds of a higher frequency only distort speech, preventing its understanding.

Usually, to isolate the client's voice from the general noise, special algorithms for digital signal processing are used, implemented by electronic chips of audio processors, for example, the firm "Motorola." Such a digital intercom device, due to the accuracy and speed of signal processing, even the first phrase transmits distinctly, without "swallowing" the first sounds.

Single-channel intercoms

This intercom device has the main electronic equipment in the console on the cashier's side. On the client side only a remote panel with a speaker and a microphone is mounted. In order to protect against vandals, the speaker is closed with a metal (usually aluminum) lining. Depending on the operating conditions, the customer's panel can also be in wind and waterproof versions with a call button, usually made in the form of a membrane, which eliminates the ingress of moisture into the interior.

If several cashiers work at the cash desk simultaneously, it is preferable to equip their workstations with "client-cashier" systems with headphones or a headset. At the same time, the colleagues' speech will not distract any of the cashiers focused only on their customers.

Multi-channel devices

The cashier (or central security post) cashier must have contact with several vandal-resistant client panels located in different locations on the fuel dispensers (or peripheral posts). Therefore, the central console must be multi-channel, and at the gas station - also provide dispatch functions by sending high-profile ads. To do this, it must have a line-out connected to an audio amplifier connected to the loudspeakers.

Multichannel intercom system "client-cashier", including communication lines with fuel dispensers and a hands-free subsystem controlled from a single central console of the filling station, significantly speeds up customer service, as well as enables the cashier to provide the requisitioners with the necessary information.

Organization of multichannel intercom

So, what kind of equipment, besides the central console and calling panels, includes a multichannel intercom? Its circuit contains the bundled switch box. It is connected by a four-wire line to the central panel. Each call panel connects to the switch box with a separate wire.

The central console of the device contains a set of numeric buttons for selecting the calling panels. In order for the cashier's messages to be clearly audible in the conditions of the gas station, these panels allow his voice to be output to the speakerphone through an external amplifier and loudspeakers made in the second category of performance - "Working under a canopy."

Features of intercoms with speakerphone

The hands-free talking device (for filling stations and other facilities) is designed with some design features to simplify the connection of the cashier with customers and refuellers. To ensure communication between the cashier and the interlocutors at a distance of several tens (or even hundreds of meters) from the remote, the microphone of his console must be highly sensitive and windproof for speech transmission with high intelligibility regardless of the source of wind noise (for example, from fans). To confidently disassemble the speech of interlocutors at a high level of noise, the central panel and the calling panels are supplied with high-volume speakers of mylar having a high specific area of the diffusers.

Popular Intercoms Commax

The single-channel Commax VTA-2D type telephone system "client-cashier" provides duplex communication (without having to press the "Transfer" buttons). Consists of two identical subscriber's sets in the form of calling panels "speaker-microphone" in plastic cases of gray color. There is a wall and desktop version of the panels. It is powered by a 12-volt DC source with a consumption of no more than 3.5 watts. Its cost is about 1700 rubles.

Also single-channel duplex device Commax DD-205 type "client-cashier" contains a cashier's console with flexible microphone attachment, electronic adjustment of its sensitivity, light and sound indication of adjustments. The device includes a vandal-proof panel of the client. The device is controlled by the Motorola audio processor. Its cost is about 6000 rubles.