A circuit arrangement for generating signals corresponding to the read points in time necessary to allow a recording unit to designationally read information contained in two serial, bit-oriented ISDN information signal streams respectively transmitted via communication lines of first and second ISDN-oriented interfaces respectively disposed in first and second ISDN equipment stations, said first and second ISDN-oriented interfaces facilitating communication between said first and second ISDN equipment stations, each of said two serial, bit-oriented ISDN information signal streams formed as a continuous sequence of bit groups, each bit group having a prescribed plurality of bits arranged in sub-groups or channels having a defined plurality of bits with a defined information content, said first ISDN-oriented interface providing a bit clock signal and a bit group clock signal to said second ISDN-oriented interface, said arrangement comprising:
- a shift register having a clock input and a plurality of storage locations respectively dedicated to said prescribed plurality of bits of a bit group, said shift register further having a shift-set input connected to receive said bit group clock signal;
- reset means connecting said shift-set input to said bit group clock signal and operable to generate a shift register reset signal from said bit group clock signal;
- said shift register further having a plurality of parallel inputs corresponding to said plurality of storage locations, each of said parallel inputs being connectible to a voltage potential representing two binary conditions;
- switch means connecting said inputs to said voltage potential;
- an AND logic gate connected to receive said shift register output and said bit clock signal, said AND logic gate having an output;
- and
- a recording unit connected to said output of said AND gate for recording the informational contents of those bits of the bit determined by said switch means.