Calcutta, July 28: The tragedy at Bidhan Nivas has nailed a myth that told generations of Calcuttans to dial 100 when in trouble.

An investigation by The Telegraph suggests that the trust-inducing three digits are largely a gateway to a communication merry-go-round for those living on the so-called “fringes” of Calcutta police’s territory.

A better option is to keep the phone number of your police station within easy reach and hope that the law-enforcers there react with the alacrity that the emergency number 100 demands. But this will not be of much help when you are on the move in the city.

Yesterday, the frantic call to 100 from a teacher at Bidhan Nivas, minutes after robbers had left the house of 88-year-old Shanta Bhattacharya who was later declared dead, did not get through to Lalbazar, the Calcutta police headquarters.

It emerged today that even if the call had gone through, it would not have reached the Calcutta police control room. The call would have been answered by a policeman at the subdivisional police officer’s office in Salt Lake, informing the caller that Bidhan Nivas was not in the jurisdiction of that centre.

The Telegraph has learnt from officials at BSNL and the police that because of a mismatch in what the telecom service provider defines as Calcutta and the areas under Calcutta police, distress calls from parts of the city regularly go to control rooms in the adjoining districts.

Bidhan Nivas is under Calcutta police but its telephone exchange is in Salt Lake, which falls in North 24-Parganas.

Even after getting through to the subdivisional office, all the caller stands to gain is an eight-digit number (2214-3230 of the Calcutta police control room), which defeats the very purpose and convenience of having an easy-to-recall emergency number such as 100.

In the absence of a technology to re-route the call to a neighbouring police district, the caller will have to memorise or jot down the number, hang up, call Calcutta and hope for the best.

All 100 dials from the telephone exchange 2334 go to the Salt Lake SDPO’s office.

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Senior Calcutta police officers admitted to being aware of the mismatch in jurisdictions and the consequent problems. “The areas on the fringes of our area, which are often part of telephone exchanges in the neighbouring districts, frequently throw up this problem,” an officer said at Lalbazar.

What he described as “fringes” is one of the most populated residential zones of the city. The officer had no answer when asked what the police had done to correct that anomaly.

Another officer said the same problem could arise if someone dialled from a pocket of south Calcutta. “The calls often go to South 24-Parganas police from those areas.”

Lalbazar frequently gets calls from the districts because of the same mismatch. “We are helpless. We have to work with the system available with us,” an officer said.

Once 100 is dialled from a landline, the three-digit number goes to the local telephone exchange and is routed to an eight-digit number specified by the police. A Calcutta telephone exchange that is also under Calcutta police would route the call to Lalbazar. Similarly, a North 24-Parganas telephone exchange can route it only to North 24-Parganas police.

Under the circumstances, it is pointless calling 100 if you live in Calcutta but your telephone exchange caters to another district.

It is also pointless calling 100 from a mobile phone if you are on the move and in danger in a part of Calcutta bordering a police district.

It means that before you make a distress call you should know where exactly you are located, where your telephone exchange or nearest mobile tower (in case of cellphones) is and the uncertainties that follow.

Technically, any call from a Calcutta police area should go to the Lalbazar control room. Eleven personnel man a console there. It means that from a population of 47 lakh, the city police can handle a maximum of 11 distress calls at a time.

Using the integrated services digital network (ISDN) technology, up to 30 calls to a single landline number can be handled simultaneously. But Calcutta police have not put the full facility to use, police sources said.

In the Salt Lake SDPO’s office, it is only 3 instead of 30.

The number 100 is uniform across the country and can be called for any distress situation — such as a fire or a medical emergency — and not just a crime, like in the US where one has to call 911.

But unlike here, the 911 emergency system is expected to respond within 60 to 90 seconds of receiving a call. The system is held so accountable that should the caller abandon the call, the line is expected to be held until the emergency service tracks down, answers and releases the call.

Jurisdictional problems are addressed by the Master Street Address Guide (MSAG), a database that cross-references telephone numbers, addresses, streets and jurisdiction, says Dispatch Magazine, which provides information on public safety communication. The MSAG is pre-programmed to take 911 calls and route them to the proper public safety answering point that will dispatch emergency personnel.

Several police officers blamed BSNL for the glitches that prevent a distress call from reaching the right police station. But BSNL officials said no official complaint had been lodged by the police.