GB1459865A - Time division multiplex telecommunications systems - Google Patents

Abstract

1459865 Automatic exchange systems SIEMENS AG 7 Jan 1974 [5 Jan 1973] 00653/74 Heading H4K A tdm system includes at each end of a signalling channel a D.C. to pulse and a pulse to D.C. characteristic converters U2, U1 arranged as a pair and which are associated with a subscriber end input E and a subscriber end output A via an arrangement of four relays C, R, I, II, associated respectively with contacts C1, C2, r, 1, 2, a power supply B, a delay element VG and a diode D, the interconnections being substantially as shown in Fig. 1. The position of the switches is shown for the unoperated state of the corresponding relay. The arrangement is used to enable the signalling channel to be seized either by exchange ES1 or ES2 and the specific arrangement of components in each station is for signalling the conditions "ready for seizure", "seizure" and "reverse blockage". Signalling between converters uses four bit binary signals but for signalling the above conditions only bits 1 and 4 are significant, bits 2 and 3 being "1" for all the conditions. In a ready for seizure state relay R is operated to apply earth to input UE2 via contact r. The condition 1110 is transmitted and earth at output UA2<SP>1</SP> operates relay II<SP>1</SP> to close contact 2<SP>1</SP>. The same condition exists in the reverse direction to hold relay II operated and contact 2 closed. To seize the channel from exchange ES input E is earthed to operate relay C. Contact C2 opens immediately removing the earth from input UE2. The condition 1111 is transmitted to cause output UA2<SP>1</SP> to go to 1 thereby releasing relay II<SP>1</SP> to open contact 2<SP>1</SP>. The channel cannot then be seized by exchange ES2. In exchange ES1 the closure of contact C1 on the operation of relay C causes earth to be applied to input UE1 after a delay determined by element VG. Condition 0111 is then transmitted causing output UA1<SP>1</SP> to go to earth to operate relay I<SP>1</SP>. Output A<SP>1</SP> is then connected directly to earth via contact 1<SP>1</SP> and relay R<SP>1</SP> releases thereby removing the earth on input UE2<SP>1</SP>. Condition 1111 is transmitted from exchange ES2 to exchange ES1 as an acknowledgement of seizure signal. Relay II is however held via diode D when the earth is removed from output UA2 on receipt of the 1111 signal. Similar operations take place when release occurs due to the removal of the earth mark or input E. It is stated that the relays may be replaced by corresponding electronic switching elements.