My E10B Tone collection some links not functional! It is also less powerful compared to the leviathans that are operational presently. To give you numbers, my E10B, at maximum capacity, can handle upto 11, circuits in a transit exchange configuration. On the other hand, an OCB can handle 60, circuits as a transit switch. But given the fact that I owe most of my knowledge to my E10B, I decided to record the tones that I heard for posterity.
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My E10B Tone collection some links not functional! It is also less powerful compared to the leviathans that are operational presently. To give you numbers, my E10B, at maximum capacity, can handle upto 11, circuits in a transit exchange configuration.
On the other hand, an OCB can handle 60, circuits as a transit switch. But given the fact that I owe most of my knowledge to my E10B, I decided to record the tones that I heard for posterity.
I used a Genius All the recordings are 8-bit,11Khz sampling rate, mu-law PCM encoded. A note of warning In spite of various efforts to reduce the filesize, the wav files still total upto 7Mb, with individual files ranging in size from 85Kb to Kb. So, get ready for some waiting if you are on a dial-up connection. My email address is at the bottom of the page. In all the tones recorded, you will first hear the digits being dialled using DTMF tone dialling.
And since my modem is dialling, the dialling is pretty fast. But rest assured, I can manually dial faster that my modem. An E10B dial tone - This is the starting point. In most exchanges, dial tones are produced by simultaneously generating two frequencies which are close, giving rise to a beat frequency that is the difference of the two frequencies.
The beat frequency manifests itself as the burr that we hear. The E10B dial tone lasts for 10 seconds and then is replaced by a busy tone. The E10B ring tone - If you notice, you will realise that the ring tone is the same as the dial tone, except that the dial tone is a continuous burr for 10 seconds, while the ring tone is a repeated burr-burr in the format given below Now, how would the ring tone be different if I were to call a subscriber who is connected to an E10B that is not my exchange?
Say, I were to dial a number within Madras which was served by another E10B. The ring tone would be the same as in the previous two cases, except that call setup time will be slightly more, since the call goes out of the exchange. Remember that I mentioned that calls to E10B numbers which were busy with another call already which had call waiting enabled , feel different?
For purposes of illustration, I dialled a number within my exchange that had call waiting turned on and was busy with another call at the time how did I know - that number was generally busy and had call waiting turned on - maybe the owner of the phone has a teenage daughter , and comparing this with the earlier recording of a ring tone within my exchange, you will see a marked delay after the end of dialling and before the ring tone starts.
You will have to play the normal ring tone recording to see the difference. And there is another example recording too. Today, most telecom operators use voice announcements to inform callers that the number does not exist, trunks are busy and so on.
But earlier, there used to be what is called a Number Unobtainable tone or NU tone. A human recorded voice says "Facility enabled" or "Facility diabled". But in my exchange, the acknowledgement is a tone - a long single frequency tone that is repeated a couple of times.
I have continued recording until the tone is repeated once. I also recorded the acknowledgement tone when I dialled 43 to disable call waiting. Some exchanges generate fast busy tones to indicate lack of available resources to serve the subscriber.
I picked up my phone on the 31st of December a few seconds after midnight the 1st of January , actually. Maybe a lot of people were making calls to their friends and relatives, and my exchange did not have any more resources dialled digits registers, free trunks etc. So it instead gave me a fast busy tone.
But to give you an idea of the fast busy tone , I recorded a call to a number that always results in a fast busy being generated instead of a normal ring tone. The number looks like any other number but for some reason, produces a fast busy. My E10B has another interesting and useful feature.
When an incoming call is a long distance call a call from another phone not within the same local billing area , the phone rings differently. Instead of the nomal burr-burr, the ring is a long burr with a short delay between successive burrs. I dialled two long distance numbers numbers not in madras and the called numbers were served by E10B exchanges how do I know? I found out, of course. Listen to long ring 1 and long ring 2. But I did not dial long distance. Well, the number I dialled was a toll-free number 1 service and the call was put through to a number that supposedly is outside Madras and hence the receiving exchange sees the incoming call as long distance and generates the long ring.
And the receiving exchange was an E10B. What happens when a call is forwarded to another number? What ring do you hear? A number within my exchange was forwarding calls to another local number served by a different exchange. As a result, the resulting call setup time was longer and the ring tone was also different. If the exchange serving the number that was receiving the forwarded calls was also an E10B, there would be no difference in ring tones.
But in the call forwarding example , that is not the case. Notice greater call setup time and different ring tone. That was my E10B tone collection. I also recorded the ring tones, fast busy tones and other call progress tones when I dialled other numbers in and around Madras, and also outside Madras and also international. Ring Tones of other exchanges.
List of telephone switches
Merge this question into. In some designs, a physical space switching layer alternates with a time switching layer. Composite switches are inherently fault-tolerant. The Bell System dial service implemented a feature called automatic number identification ANI which facilitated services like automated billing, toll-free numbersand service. These used a crossbar switching matrix with a fully computerized control system and provided a wide range of advanced services.
E10B EXCHANGE PDF
Two types of memory was used. Program and Data Store used to store Software and infrequently changed data was implemented using a technology called piggy back twistor - in modern parlance a write once, read many times non-volatile memory system. As was the case with the 1ESS systems, processors and memory were duplicated with automatic comparison of processing results and automatic recovery in the event that a mismatch was discovered. It did not however support the complex recovery mechanism provided in the 1ESS where a processor from one half of the complex could be connected to a mix of memory both call store and program store modules from both halves of the complex in order to achieve a working combination. Processor diagnostics would generally narrow a problem down to a board or three. Connection was made via a crossbar switch. A SP1 2-wire variant was also available that provided Centrex services.
Net In United States telecommunication jargon, a central office C. Archived from the original on 10 February By the s, automatic number identification had been retrofitted to nearly all step-by-step and crossbar switches in the Bell System. The subscriber could receive calls but could not dial out. A telephone exchange is a telecommunications system used in the public switched telephone network or in large enterprises. Automation replaced human operators with electromechanical systems and telephones were equipped with a dial by which a caller transmitted the destination telephone number to the automatic switching system. The operator would be disconnected from the circuit, allowing her to handle another call, while the caller heard an audible ringback signal, so that that operator would not have to periodically report that she was continuing to ring the line. These facilities almost always had concrete floors.