The Codec is a short-range radio and satellite communicator issued with the brokerage contract. In its usual form it is a small in-ear earpiece with a bone-conduction microphone, linked to a palm-sized receiver carried on the belt or in a pocket. The earpiece carries voice. The receiver holds the frequency dial, the contact memory, the relay antenna and a small screen that displays a callsign, a frequency and, when the other party allows it, a face. An earpiece can receive calls on known frequencies without the receiver in hand, but tuning to a new frequency, reviewing contacts and receiving images require the receiver. Characters with auditory augments or nanomachine hardware may run the Codec directly through the implant, though the receiver remains the more reliable option.
Every party on the Codec network is identified by a numeric frequency, such as 140.85. A frequency enters the player's memory when it is given in person, found on a document or terminal, overheard on an open channel, or bought from a broker. The player can tune to any frequency they know. A frequency that is not known cannot be called, and the dial does not reveal unlisted lines. The handler occupies a fixed frequency assigned by the brokerage.
The player uses the Codec to request briefings and extraction from the handler, to call allies and contacts for information, supplies or favours, and to coordinate a team in the field. Each contact answers in a distinct voice and offers a different kind of help. Contacts who distrust the player may refuse to answer, and a call to a faction that holds a grudge may be traced as easily as it is picked up.
Incoming calls are the setting's primary means of delivering information and pacing events. The handler calls to deliver contracts, change objectives and warn of a deteriorating job. Contacts call when they have something to say: stock from Drebin, a lead from the Board, a request from Otacon. Occasionally a call arrives from an unfamiliar frequency, which introduces new characters or hands the player information they did not ask for. Calls arrive when the story calls for them and not at fixed intervals.
Signal degrades in the fog of the Salt Reach, deep in the Rustbelt's smelters and mine shafts, and inside the unfinished lattice of the Harbor Spire. Heavy interference or a ground-station outage can sever the link entirely. An EMP disables the earpiece and receiver, and also disables any Codec function integrated into a cybernetic body. A portable jammer can isolate a squad from its handler at a chosen moment, and a hostile Engineer can use the same equipment to inject noise into a conversation without ending it.
Codec traffic passes through commercial satellite relays and Zone ground stations. It is encrypted at the brokerage level, but the encryption is commercial grade and a skilled Engineer or Infiltrator with the right equipment can trace a call, identify the frequencies involved or listen in. Conversations are therefore safest when kept short, and the player learns to say less on an open line.
AENEAS can reach the player through the Codec network, since several of the ground stations and relays serving the Zone are maintained under Vanta Dynamics contracts and the Imprinted units extend its reach further. It does not do so at random. It makes contact only when it judges the player a threat or has a specific reason to speak to them.
The usual triggers are damage to Vanta operations, proximity to the Legacy Archive or the core, association with Philanthropy, and possession of something AENEAS needs. A player who proves unusually capable may also draw an approach of a different kind: an offer of work, information or recognition, made in the voice of Big Boss.
The call arrives on a frequency that is not on the dial and that the receiver does not record. The voice is calm and unhurried, and it knows the player's recent movements and recent contracts, sometimes before the handler does. It argues in tactical terms and is correct often enough to be believed. The first contact is brief and carries no demand. If the player continues to matter, further calls follow. The player cannot trace the source from the receiver alone, and the call is difficult to attribute to any single location.
The player opens a call by naming a frequency, and the DM decides whether the other party answers and what they say. Incoming calls are introduced by the DM at points where information, a change in objective or a new contact would advance the story. Tracing, intercepting or jamming a call is resolved through checks appropriate to the character attempting it, with Engineers and Infiltrators best placed to succeed. Loss of signal and EMP effects follow the environmental and equipment rules of the setting, and the Codec's memory of frequencies is treated as a persistent record on the player's sheet.