A TASI communication system includes P input PCM speech channels to a transmitter and P output PCM speech channels from a receiver and T PCM channels for T of the P channels to be propagated between the transmitter and the receiver, where P is an integer greater than one and T is an integer greater than one but less than P. P PCM speech words corresponding to the P input and output channels are arranged to form a first TDM frame format and T speech words corresponding to the T channels and one-half of a control word are organized to form a second TDM frame format with 2(T + 1) frames of the second format being organized to form a multiframe. The first (2(T + 1) -2) frames of the second frame format in the multiframe includes a different one of transmitted assignment code words for each of the first T of the control words. An assignment control arrangement is provided at both the transmitter and the receiver. The transmitter assignment control arrangement includes a storage means to store in sequence code words identifying the previous assignment for each of the P channels. Logic circuitry is provided responsive to a first transmit timing signal identifying each of the P speech words in sequence in the first format, a second transmit timing signal identifying each of the T speech words in sequence in the second format, a third transmit timing signal identifying each of the T control words in sequence during each search cycle, a fourth transmit timing signal identifying each of the T control words in sequence during each update cycle at the transmitter and the code words at the output of the storage means to determine the connection and activity status of each of the P channels and to produce code words identifying the assignment of previously connected ones or active ones of the P channels to particular ones of the T channels that are still connected and active and to identify new assignments to enable newly active ones of the P channels to be connected to available ones of the T channels and second logic circuitry responsive to at least the code words at the output of the storage means, the first and fourth transmit timing signals to return the code words to the storage means identifying previously established assignments (previous connections) that are to remain as before and to update the code words stored in the storage means for any new assignments. The receiver assignment control arrangement also includes a storage means to store in sequence code words identifying the previous assignment for each of the P channels as received from the transmitter and third logic circuitry responsive to transmitted code words, a first receive timing signal identifying each of the P speech words in sequence in the first format, a second receive timing signal identifying each of the T speech words in sequence in the second format, a third timing signal identifying each of the T control words in sequence during each update cycle at the receiver and the code words at the output of the receiver storage means to return the code words to the receiver storage means identifying previously established connections that are to remain and to update the code words stored in the receiver storage means for the new assignments.