Before the mobile revolution the red telephone booth, or box as it was popularly called, was a regular part of the Australian streetscape. These boxes were used whenever people went out and in some cases it was the only telephone people had.

To make a call you walked to the nearest box and hoped it was vacant. If it wasn't you would encourage the person inside to stop talking by pacing nervously outside.

One estimate is that at least 40,000 boxes were manufactured in Australia, originally by the PMG (Postmaster-General's Department). Of those, as few as 1000 are thought to have survived. One of only a handful still operating on a street is in The Rocks in Sydney.

In the 1980s hundreds of boxes were sold to the public by Telecom (as Telstra was then known) when these were replaced by the modern metal-framed units.

The wooden ones, some close to 80 years old, are often left to rot in backyards. Now any in good condition are collectors' items. Some of the rarest models, like the double boxes, fetch up to $50,000 in restored working order. Even the more common Temperate dome roof models are now worth up to $5500 in fully restored condition.

There's no shortage of telephone box enthusiasts. These utilitarian structures hold a strong emotional appeal for many baby boomers. One man bought a restored box because he proposed to his wife in one – it was installed to commemorate their 20th anniversary. Other couples have admitted to other forms of intimacy inside a box. What is interesting now is how many people want to place their restored box indoors to keep them better preserved. The original phone units can be converted to modern circuitry by telephone restorers and modified to operate without coins.

The public telephone box is a relatively modern concept. The first red English model was designed in 1924 by Sir Giles Gilbert Scott. He chose the colour to make them easy to spot regardless of weather.

At first our boxes were made of imported maple but Australian conditions and white ants led to the introduction of tougher materials like ironbark and blackbutt.

The climate also played its part. Early designs had little ventilation and tended to rot quickly. Modified versions with vents were introduced in the early 1950s. These are known as the Vented models.

The NSW Temperate style features the iconic dome roof with slanted glass louvres for ventilation. The roof was originally made from bonded asbestos and concrete painted white with black trim but took on many colour designs over the years.

Restoration is a tricky business best handled by a professional. It's important to use authentic woods as modern kiln-dried timber is not suitable.

Finding the original phone unit is difficult but not impossible. These are not cheap. The early dark green units known as Penny Long Toms cost up to $1800 complete. The later A/B coin meters with wall phones are worth about $1200.

Even if you only want the box you'll probably want some modifications. If you don't want a roof containing asbestos, replacements are made in fibreglass. The original lead-based paint can be replaced by something less toxic.

One thing usually left alone is any original graffiti. Most old boxes have a variety of names, numbers and messages gouged into the wood – one noteworthy example is "Ring Matt for bad sex".

One thing best removed is the traditional phone-box smell – a potent mixture of dust, cigarette ash and urine.

Phone boxes sometimes appear on sites like eBay and whatever their condition are usually priced optimistically. Demand exceeds supply and the lowest price seen recently was $600 for one suitable only for parts. One dated 1950 and described as in working order was advertised in the ACT for $2500, complete but unrestored. Those wanting to buy one that hasn't been restored are advised to first check there is no damage to the roof or base for safety reasons.

The PMG had identification numbers and call signs on their boxes so authenticity can be checked.

There are telephone museums in Sydney and Melbourne run by volunteers who can advise. The Victorian Telecommunications Museum is in Telstra's Hawthorn telephone exchange. Sydney's Telstra Museum is in Kitchener Parade, Bankstown. Curator Brian Mullens will be happy to show you around.

My collection

Justin O'Connor bought his first phone box when he was 15 and has been collecting ever since, so it's no wonder he's now known as “the red telephone box guy”. He has since turned his hobby into a business, restoring and selling old boxes from Jervis Bay in NSW.

At last count he had about 40 of them, some complete, most in pieces ready to be used for restoration. His pride and joy is one of the very rare 1930s hardwood floor model double flag boxes. He also has examples of every phone unit used in public boxes.

He sends his restored boxes around Australia in flat packs, where they often end up installed indoors. Two of his red boxes now sit inside an office on the 16th floor in Sydney. Others are in Malaysia, Britain and the US.

O'Connor says he and his fellow enthusiasts are dedicated to saving as many surviving boxes as they can. For more details see redtelephonebox.net.

$4250

This box design is known as a 1960s NSW temperate dome roof. A common sight on our streets until the 1990s, there are now few examples in good working condition.

$7000

The 1950s "vented" Tasman flag style was an improved version designed with Australia's hot conditions in mind.

$8500

The original, fully glazed PMG Tasman flag style was introduced in 1930-40s. There are thought to be as few as 100 of them left in Australia.