Old fashioned wake up calls
How did the hotel personnel used to make their morning wakeup calls before computers and electronic devices became available? Their tool was a patented electric clock named James Remind-O-Timer.
The 
James Remind-O-Timer was invented by a taxi driver named Henry C. James, Jr who had several regular fares and he needed a reminder to get him to the clients on time.
It was a useful innovation for people in various industries, from hotels to taxi services to laboratories. The Remind-O-Timer was used in all high class hotels so front desk personnel could remember to make their morning wakeup calls in a timely fashion.
The electric clock’s unique feature was its mechanism with 48 small keys located around the face of the clock that could be set to ring a maximum of 48 alarms or ‘reminders’ at one setting. It also featured a sweep second hand and regular clock features, allowing you to tell the time of day as well.
Henry established the James Clock Manufacturing Co. in Oakland, California in 1933, and produced and patented his innovation in 1937. The company created models for the blind as well, and was in business until 1987.