You don't not need to book tickets for the Cable cart. Here is some info, if this helps: Anyone holding a valid paper Travelcard, Oyster Travelcard, a London Boroughs Freedom Pass, or using Oyster Pay-as-you-go, gets a discount of 25% off the fares below.
The duration of a single crossing is ten minutes (reduced to five minutes in rush hour as the service speed is increased). With a capacity of 4,080 passengers an hour, 62,000 per day and up to 500,000 people a week in summer.
It's a cable car over the river, rather than a tram (just to avoid any confusion). You can use PAYG money on an Oystercard to pay for it, but it won't count towards the daily cap.
It's easy to find and board a cable car. Choose from three cable car lines - two start at Powell and Market and continue to the Fisherman's Wharf area; one starts at California and Market and continues to Van Ness Avenue.
It is not necessary to book the cable car. You can just turn up and use either your Oyster card or bank card on the reader, just as you would on the bus or tube. I also found there was no difference in price whether you booked in advance or paid on the day.
The car will then slowly move forward, and a further, and stronger, pull locks the grip to the cable and brings the car up to its cruising (and maximum) speed, of 9.5 mph. To stop the car, the grip lever is thrown forward to disengage the grip, and the hand brake lever pulled on.
if it started at 7, it could end at 7:45, or 9:00, or 2 in the morning. That could be true if it started at 6 or at 3:30. It ends when it ends. But a typical concert runs about two hours, with an intermission of 15 minutes in the middle.