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.
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).
Hold Invader
Allows remote audio to still be passed while the called party thinks they are on hold.
Wrong Number Generator
Outputs the DTMF digit '8' after receiving a valid DTMF digit '4', approximately 75% of the time.
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)