times in order to carry out general household errands, such as food shopping and laundry. Offenders may have to respond to communications from a higher authority to verify that they are at home when required to be. Exceptions are often made to allow visitors to visit the offender. The types of house arrest vary in severity according to the requirements of the court order. A curfew may restrict an offender to their house at certain times, usually during hours of darkness. "Home confinement" or detention requires an offender to remain at home at all times, apart from the above-mentioned exceptions. The most serious level of house arrest is "home incarceration", under which an offender is restricted to their residence 24 hours a day, 7 days a week, except for court-approved treatment programs, court appearances, and medical appointments. In some exceptional cases, it is possible for a person to be placed under house arrest without trial or legal representation, and subject to restrictions on their associates. In some countries this type of detention without trial has been criticized for breaching the offender's human right to a fair trial. In countries with authoritarian systems of government, the government may use such measures to stifle dissent. Using technology for enforcement In some countries, house arrest is enforced through the use of technology products or services. One method is an electronic sensor locked around the offender's ankle (technically called an ankle monitor, also referred to as a tether). The electronic sensor transmits an RF signal to a base handset. The base handset is connected to a police station or for-profit monitoring service. If the offender goes too far from their home, the violation is recorded, and the police will be notified. To discourage tampering, many ankle monitors detect attempted removal. The monitoring service is often contracted out to private companies, which assign employees to electronically monitor many convicts simultaneously. If a violation occurs the unit signals the office or officer in charge immediately, depending on the severity of the violation. The officer will either call or verify the participant's whereabouts. The monitoring service notifies a convict's probation officer. The electronic surveillance together with frequent contact with their probation officer and checks by the security guards provides for a secure environment. Another method of ensuring house arrest compliance is achieved through the use of automated calling services that require no human contact to check on