field telephone

Wired field role

Recognition requires evidence of a wired voice endpoint intended for field deployment; appearance and current location are insufficient.

1. What documented purpose and interface identify this equipment as a field telephone? definition
2. Is the item a complete telephone endpoint, a handset accessory, a radio or a switching device? boundary

Configuration evidence

Design designation, revision and fitted handset or accessories determine which instructions can safely be applied.

1. Which markings and component identifiers establish the design and configuration? provenance
2. Which manual or technical record applies to this configuration, including modifications? provenance

Speech circuit operation

The model records how speech is transmitted and received, including any required handset switch or mode setting.

1. Which circuit mode and handset controls are required for two-way speech? definition
2. What documented test establishes intelligible transmission and reception independently? action

Power dependencies

Each function needs an explicit power dependency, permitted supply and assessment method.

1. Which functions require local batteries, line power, a hand generator or another documented source? definition
2. What voltage, polarity and loaded-supply measurements establish acceptable operation? measurement
3. Which replacement cells or external supplies are approved for this design? action

Call generation

The outgoing call signal must be identified and matched to the receiving endpoint or switchboard.

1. How does the operator generate a call signal in each supported operating mode? action
2. What signal voltage, frequency or other interface parameters are specified, and under what load? measurement

Call state behaviour

Alerting, answer and clearing behaviour are configuration-dependent and must be distinguished from speech operation.

1. What indicates an incoming call, and what controls or settings can disable that indication? definition
2. What actions answer and end a call, and does the connected switchboard require a separate clearing signal? action

Compatible circuit

A valid connection requires agreement on conductor arrangement, power, speech interface and signalling.

1. Which terminal assignments and conductor arrangements are supported by the applicable documentation? definition
2. What evidence establishes compatibility with the proposed remote telephone or switchboard port? provenance
3. Does the proposed connection need an adapter or interface outside the telephone's own boundary? boundary

Usable line envelope

Any distance claim must retain its cable, circuit, supply and test conditions, with speech and signalling assessed separately.

1. What loop resistance, insulation condition and attenuation are measured for the proposed line? measurement
2. Under which cable and operating conditions are the documented speech and signalling limits valid? provenance

Deployment suitability

Suitability requires evidence for the complete operating configuration, including open covers, connected leads and environmental exposure.

1. What carried mass, dimensions and environmental limits apply with the required accessories fitted? measurement
2. Which documented checks and precautions address ringing voltage, foreign line voltage and weather-related line exposure before connection or repair? action
3. Which issuing body, standard edition and test record support any claimed protection or certification? provenance

Serviceability evidence

Readiness follows configuration-specific checks of power, speech, signalling and physical condition; unresolved faults remain explicit.

1. Which approved checks distinguish battery depletion, handset or cord defects, signalling faults and an external line fault? action
2. Which observed defects require cleaning, approved component replacement, specialist repair or withdrawal from service? action
3. What test results and remaining limitations justify the recorded readiness state? measurement

Check these first

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these check these first hold for the sense of field telephone this model covers, and on what evidence? provenance

Kinds and varieties

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these kinds and varieties hold for the sense of field telephone this model covers, and on what evidence? provenance

Identifiers and schemes

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these identifiers and schemes hold for the sense of field telephone this model covers, and on what evidence? provenance

Real-world use

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these real-world use hold for the sense of field telephone this model covers, and on what evidence? provenance

Failure modes and hazards

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these failure modes and hazards hold for the sense of field telephone this model covers, and on what evidence? provenance

Regional variation

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these regional variation hold for the sense of field telephone this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Recalled without web access and unsourced; every item is a lead to verify.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of field telephone this model covers, and on what evidence? provenance