View source for Closed Circuit Telephone Systems

A '''Closed circuit telephone system''' acronymed to CCTS is a group of telephones that are wired to each other instead of using an external telephony service provider. [[Spacesim]] uses a CCTS for its primary [[CAPCOM]].

==Basic System==
A telephone junction box usually has four wires, of which the Green and Red wires carry content. If the red and green wires of two telphones are wired in parallel with a power source, they will be able to communicate. This is the most basic CCTS setup, and was employed in the [[Habitat#History|Brahe]].
<pre>
 .--\/\/-.----. 
 |       |    | 
 _       |    | 
---     { }  { }
 |       |    | 
 ._______|____| 
</pre>
Where {} represent telephone jacks.

With appropriate voltage, this system could be scaled to any number of telephones wired in parallel.


==[[Simulator]] Tie-In==
The simple addition of a single-pole single-throw switch in series with a telephone, would allow the [[Simulators]] to disable it from talking to the circuit, as such:
<pre>
 .--\/\/-.----. 
 |      /    / 
 _       |    | 
---     { }  { }
 |       |    | 
 ._______|____|
</pre>
Where the / are the switches.


==Multiple Circuits==
The system deployed in the [[Hawking III]] employs all of the principles discussed above, but expands the system to employ two separate circuits. The first circuit is an inter-[[Habitat|Hab]] circuit, and the second is a Hab-[[Mission Control|MC]] circuit. All phones on the same circuit will be able to talk to each other. The simulators will be able to disable each phone from either circuit individually, with the exception of the phone in the [[Simulator Loft]] and the connection to the [[VPN]]. However, to accomplish the equivalent effect, the simulators could disable all phones in the Habitat from the Hab-MC Circuit.

Each circuit has its own power supply and resistor to act as a load in case no phones are attached. The MC Phone is wired directly into the MC Circuit, whereas each Habitat phone is wired to a double-pole double-throw switch that will allow it to choose which circuit it will connect to.
<pre>
      HABITAT         ~      MC
 .--\/\/-- \-<  ^  >-/  -.--\/\/--.
 |              |        |        |
 _              |        |        _
---            { }      { }      ---
 |              |        |        |
 |              |        |        |
 |___________<  ^  >_____|________|
</pre>
Where the {} are telephone jacks, \ / are single throw switches, and <^> are double throw switches.

In the actual system, there are five telephones that duplicate the example phone that is connected to the double throw switch. Only one is shown here for clarity.

The final design, which is being implemented for the [[2009-10]] [[Mission]] is a modified version of the above circuit that uses only one power supply.

<pre>
 .--\/\/---< ^      A
 |           |
 |          { }     P (Phone)
 |           |
 .--\/\/---< ^      B
 |           |       
 _           |
---          |
 |_________<<       C   
</pre>

Apologizing for the complete unclarity of the above circuit diagram, it attempts to show that the circuit is split into two parallel systems right after the power supply with the switches wired so that they will choose between one of the two systems as opposed to one of two circuits in the earlier version of the circuit.

If the bottom of the double pole double throw switch appears as below, then each prong will be wired to the appropriately labeled wire in the above diagram.

<pre>
A<    >C
P<    >P
B<    >C
</pre>

==Analogue to Digital==
[[Mission Control]] was run from the [[Sim Office]] at [[Lisgar]] during [[Daedalus]] as opposed to being run from [[440 Albert]]. In order to pass data to and from the simulation facilities at 440 Albert, the [[OCDSB]] provided a [[Virtual Private Network]].

It was discovered that by connecting a Whetstone Bridge to the CCTS with a phantom telephone represented by a mini cable taking the place of the fourth resistor in the Bridge, a signal could be passed to the computer.

However, a solution to have the line-out from a computer to the telephone system was not discovered prior to [[Daedalus]], and the CCTS system was not deployed for that Mission.