"When you want the correct time, just call Capitol 7171!" This 1940s advertisement promotes Houston's time service, a telephone number that Houstonians could call to hear an operator say the time. Funded by national and local advertising, the operator always begins the message with a product promotion. According to the advertisement, more than 150,000 telephones existed in Houston at the time, with some 75,000 callers using the time service every day.