IDEA - Phones and Radios
Not the usual music radios, but stuff like talkshows, pirate stations that set out encoded broadcasts, propaganda speeches and pro-communist rhetoric. People running the stations could wait for people to tune in, have a way to play some music, then speak icly through the radio stuff like 'Hans has picked up half a dozen eggs and is home safely. Ana has donated to the local food drive and wishes for more people to eat.' stuff like during the German occupation of France where the BBC would broadcast those messages disguised as personal messages to their friends and others.
Phones
Land lines people can have set up where you can dial numbers and get stuff like - Stasi/polizi HQ, offices of Officers and Stasi officials (reserved for communications over the phone instead of in person), anonymous tip lines about pro-western activity. This could add the opportunity for secretaries, phone operators, give a way for civilians to call in activity without being seen going to a stasi/policeman and dropping their info, and also a way to privately do such and maybe get an extra ruble/mark or ration thrown your way. This could also have phone booths, engineers and civilian contractors that install landlines/maintain telecommunication infrastructures for radios and phones, raids on pirate radios, anonymous threats.