The LOD/H Technical Journal, Issue #3: File 08 of 11 __________________________________________________________ @@ @@ @@ Coin Service, The Central Office, and You @@ @@ @@ @@ by @@ @@ @@ @@ Phase Jitter @@ @@ @@ @@ Legion of Doom! @@ @@______________________________________________________@@ In this file I will attempt to give a basic overview of how various central offices handle coin service. If you feel your interest grows due to this file there are other good technical documents about coin service, i.e. Bell System Practices, CDs, PDs ect.. Coin service is differentiated from other services by a special class of service. All switching systems give -48 volt battery toward the coin phone on the ring side of the line. Coin-First lines have an open TIP during a normal receiver-on-hook condition. When a line goes off hook the central office takes no action and in fact can not detect the off hook condition due to the line's conditioning-for-ground start. When the customer deposits money the coin ground is extended to the ring side of the line. The ground signals the line equipment in the central office as a to give a dial tone. Dial-Tone First offices give both the battery and ground to the coin station, thus providing a dial tone equivalent to a POTS phone. All coin service is super current sensitive. (The central office must give at least 23 milliamps of line current and 41 milliamps of coin control current to the farthest coin station.) The switching systems differ in the method which calls are handled. No. 5 Crossbar The No. 5 crossbar coin-first offices must have a dual wound line relay with both windings in series when dealing with a coin first situation. If any Coin-First lines are served in a No. 5 crossbar office the originating registers must be able to desensitize the (pulsing) L relay by providing a resistive ground throgh its tertiary winding via the coin class of service relay. Crossbar offices can give coin return from Originating Registers, TSPS/Cordboard trunks, Ring and Tone trunks, Announcement trunks, and Coin Supervisory circuits. Coin collect current is only given through TSPS/Cordboard trunks and Coin Supervisory circuits. The only circuit that can handle a stuck coin test is the coin supervisory circuit. Crossbar offices handle coin actions on locally completed calls in the coin supervisory circuit (CS). All trunks must have access to the CS circuit or use coin junctors or coin 1A0 trunks that have such access. The use of coin junctors or coin 1A0 trunks elimnate the need for other trunks to be hard wired to the Coin Supervisory Link. When the trunk's supervisory relays show a coin action is needed the trunk searches for an idle Coin Supervisory Circuit through the Coin Supervisory Link. The bridged connection allows the Coin Supervisory Circuit to give the proper collect or return current toward the coin telephone and test to see if the action was successful. Crossbar offices handle coin actions required by DDD calls or TSPS operators in the No. 5 crossbar TSPS trunk. The TSPS base unit signals the No. 5 office by either frequencies or multiwinks. The No. 5 office receives these signals and the trunk applies one pulse of coin collect or return or ring back. The No. 5 TSPS trunk dose not make a test to see if the required coin action is successful. If the coin is still present the call is dropped and the coin remains in the trap. ESS ESS offices provide all coin control actions from the Coin Control Circuit. The Coin Control Circuit is switched to a customers line under program control. The Coin Control Circuits always make a stuck coin test at the end of a call. ESS offices handle coin actions required by DDD or TSPS operators by scanning the TSPS trunk looking for any control signals from the TSPS base unit. When the ESS office sees a request on the TSPS trunk the ESS office opens the talking path and attaches a multifrequency (MF) reciever. The MF reciever looks at the tones being sent from the TSPS base unit transmitter and checks if the signal requested is a coin collect, coin return, ring back, or operator attached. Dial-Tone First (DTF) offices not equipped with expanded In-Band Signaling give +48V talk battery during operator attached and 48V talk batttery during the rest of the call. If the TSPS signals for coin return the ESS office will open the talk path again, release the MF receiver and switch the line to the Coin Control Circuit which applies -130V coin return potential. After the coin control function is finished the system will make on recycle attempt if the coin ground is still present. Local calls are handled within the ESS machine. When a coin control function is required the program momentarily opens the talk path and switches the line to a Coin Control C cuit which applies the required current. Step By Step Coin lines in a Step By Step area are served on dedicated Line Finder groups. The Line Finders are hardwired to a coin box trunk and then cabled to a first selector appearance. Step By Step offices can give coin return from coin box trunks, TSPS/Cordboard trunks, and other miscellaneous trunks. (My knowledge of Step By Step is vague, it's kind of like trying to research dinosaurs.) Step By Step offices handle coin actions on local calls in the coin box trunks. The coin box trunk applies the coin control current through the winding of a relay to the coin station hopper trigger ground. When the coin station ground disappears, the coin box trunk relay releases and allows the connection to restore to normal. Some Step By Step offices have a timed release circuit that will time out after about eight attempts of coin control action, peg the stuck coin register, then release. If the timed release circuit is not provided and a coin ground can not be removed, the circuit must be manually released. Step By Step offices handle coin actions required by DDD calls or TSPS operators in the Step By Step TSPS trunk. The TSPS base unit signals the Step office by either frequencies or multiwinks. The Step office trunk recicves these signals and trunk applies one pulse of coin collect, coin return or ring back. The trunk does not make a test to see if the action was successful. If a DDD call was completed to a busy number the Step By Step TSPS trunk will apply one quick pu e of coin return toward the coin station, then the coin box will check to see if the coin ground has disappeared. If the ground is still present the coin box trunk will repeat the attempt to collect the coin. If you have any further questions about how the central office handles coin service or about coin service in general, I can be reached via E-mail on The Phoenix Project at 512/441-3088. Oct 1988 - Phase Jitter....Legion of Doom/Hackers!  Downloaded From P-80 International Information Systems 304-744-2253 12yrs+