Homebrew your own simple phone line harassment devices, like those sold in "spy shops" for hundreds of dollars.
Phone Line Disabler
Disables a phone line. Target can't call out and any calling party will receive a busy signal.
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Phone Ringer Disabler
Prevents a phone from ringing on incoming calls. Target can still call out but any calling party will receive no answer (unless you pick up the phone accidently).
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Hold Invader
Allows remote audio to still be passed while the called party thinks they are on hold.
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Wrong Number Generator
Outputs the DTMF digit '8' after receiving a valid DTMF digit '4', approximately 75% of the time.
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Disconnected Number Message Generator
Disables the ringing of the incoming phone, and plays back a "This number has been disconnected..." intercept recording via a voice recorder IC. You'll need to record your own message.
- Disconnected Number Generator Schematic
Datasheets
- CD4538 Dual Precision Monostable Multivibrator (140k PDF)
- LM567 Tone Decoder (303k PDF)
- MPS-A92 High Voltage Transistor (75k PDF)