[throwaway848492]

When I was a student (around 1998/99) I had to buy a mobile phone, but could not afford a subscription.

Fortunately we only pay for outgoing calls in my country, otherwise it would have been too expensive.

I bought a prepaid sim card, that had an expensive cost per minute (almost $1). I would call my parents landline once, as a signal to call me back.

It's one of the main reasons why SMS was the preferred communication methods between students, because calls were too expensive. This habit continued when we grew up, and now almost nobody calls each other. I guess the phone companies didn't think of that scenario...

[sokoloff]

Back in the early 80s (before caller ID), we’d use a collect call.

  “Do you accept the charges from <XYZ>?”
  “No.” <then place  a call to a known number in the other direction>

[jsnell]

I don't get it. If the collect call from A to B is accepted, B pays the cost of the call. In your scenario B instead calls A directly... and B still pays the cost. Where's the savings here?

(And there's a pretty clear downside to this. What if it's an actual emergency from a different phone than the standard. E.g. the only time I can remember answering a collect call, it was my sister calling from a foreign hospital after a serious accident. Trying to call back at a different number wouldn't have been great. I guess you could have a protocol involving multiple collect calls, and hope that there's no record that the first one was rejected.)

[myself248]

The A-B collect rate might be $3/min because collect calls carry absurd, insane, incomprehensibly whackass surcharges.

The B-A call back rate might be $0.20/min because it's just a normal call, not subject to the above fees.

There's the savings.

[sokoloff]

"Collect call from Bob Weaddababyeetzaboy" : https://www.youtube.com/watch?v=9JxhTnWrKYs

[failrate]

We had more subtle encoding, but important messages could be sent by collect calls that would definitely be refused.

[woleium]

Collect calls carry an additional operator fee, unless rejected.

[7thaccount]

I made a collect call (~several states away) home when I was a kid and didn't have a cell phone. I forgot all about that. I feel old now. I remember my dad had to accept and kept it short to reduce costs even though I'd been away for weeks.

[M_bara]

Back in the day ~23 years ago. A telco that had just launched started providing voice mail service. Normal outgoing call rates were about .5 usd per minute. The newly launched voice mail service was free. So university students found a new trick to call their friends, flash your friend (single ring signal to say that they don’t pick up their phone), hang up and call again, let it ring till it goes to voicemail, leave a long message, hang up and wait for the reply. Obviously it’s not full duplex and latency was high but what the e heck it’s free. The telco killed it within 2 days… and then we started having fun with all those smsc Center numbers from all over the world…