When Israeli father Avi tried to register his six-year-old twin daughters for his local ultra-Orthodox school this year, he was happy to sign a form saying his children did not watch television or use the internet at home.
But he was surprised to discover he had to give a "kosher cellphone number". He did not have one.
Avi lives in Har Nof, one of the main ultra-Orthodox, or Haredi, neighbourhoods of Jerusalem.
The community separates itself from mainstream society through its traditional religious practices and distinctive attire of black hats, coats and sidelocks for the men and long skirts and sleeves for the women.
Like most other men in his community, Avi studies the Jewish scriptures daily, keeps the Sabbath and eats only kosher food.
But he has not yet opted for the new religious adaptation to modern technology that has swept the Haredi world in Israel.
The kosher cellphone looks like an ordinary cellphone, can make and receive calls, and may have a calculator and alarm clock.
But it cannot send or receive text messages, browse the internet or take photos - all activities that could potentially involve behaviour considered "immodest" among Haredis.
For example, SMS capability could lead to the unwitting receipt of mass text messages publicising secular events. It could also be used as a method of illicit communication between male and female teenagers.
And all photos of women are forbidden, as is accessing websites with content deemed inappropriate.
The phone's other defining feature is a rabbinical stamp of approval, similar to those seen on kosher food items.
All the major Israeli cellphone companies have accommodated the powerful Haredi constituency by providing kosher phones, and cheaper-than-normal packages which connect only with other Haredi numbers.
As the companies have created distinct code prefixes to accompany the kosher phone plans, the phone numbers have quickly become a badge of religious observance.
Not only do some Haredi newspapers refuse to publish ads with non-kosher phone numbers, but parents are worried their children will be blacklisted by the shadchan, or matchmaker, if their numbers are not kosher.
"What do you associate with the Haredi community? You wear black trousers, a white shirt and some sort of hat, but today the things that define you have changed," says Avi.
He says he feels there is a sense that anyone who does not have a kosher phone "should be excluded from society".
"If you say you are associating yourself with us, please act according to our codes, otherwise do not call yourself Haredi and do not send your kids to our schools."
But while they have managed to adapt the cellphone to their lifestyles, Haredis have had a harder time with the internet.
Last year, an Orthodox rabbi and an Israeli technology executive established an internet service provider (ISP) called Rimon, which claims to be the only filtering service provider in Israel that offers customised surfing packages.
The company says it cuts out pornography, violence, and gambling, and then provides the user with five levels of further filtering, from the "protected" level that blocks images of women in intimate apparel to the "hermetic" level, which allows users to view only unchanging, vetted websites such as encyclopaedias.
"If your kid puts 'banana' into Google, some of the first sites he'll get are porn," explains chairman Moshe Weiss. "Put banana into Google on Rimon, and you get all the same sites without the porn."
One Haredi sect, the Belz, which normally forbids online access, has partially endorsed the use of Rimon, but only for those who need the internet for business purposes.
The general rule for the local Haredi community still remains no radio, no TV, no internet and no movies - though Rimon is hoping that once it starts targeting the Haredi market that will change.
For now, its 15,000 subscribers are mostly secular and modern Orthodox.
Miriam, a teacher living in Jerusalem, is one of many Haredi Jews who do not have home web access.
She expresses concern over the amount of time people devote to surfing the net, wasting time they could spend learning Torah or doing good deeds.
Her main worry, however, is over the lack of control over content.
"There are many things on the internet that are not appropriate for me as a Haredi woman, things I would prefer that my family and I didn't see or hear, like violence, pornography and inappropriate sexual relations," she says.
For Haredis, "inappropriate" means any physical contact between a man and a woman who are not married.
But Avi, who says he needs the internet for his work in the tourist industry, has unfiltered online access.
"I'm not afraid of the negative aspects because I grew up with internet and I feel I can control myself not to use the bad features," he says.
"But do I trust my children?" he wonders aloud.
"When they are old enough to use it I will definitely have to re-evaluate. I think then I might put filters on or use Rimon, or maybe then I'll even disconnect internet from the house altogether. It's just not worth the risk."