paster
A diagram of the circuitry of a telephone, glued inside the telephone itself.
paster: the wiring diagram glued inside your phone
A paster is a printed or drawn schematic diagram of a telephone's internal circuitry and connections, mounted directly inside the phone's housing. It serves as a visual reference for technicians, engineers, and repairers who need to understand the signal path, component layout, and wire routing without dismantling the entire unit. The diagram is typically glued to the inside of the phone's body, usually on the underside of the handset cradle or on an interior panel, where it remains accessible during maintenance work.
The paster shows the arrangement of components such as the switchhook, dial mechanism (or keypad contacts in later models), receiver and transmitter elements, ringer circuit, and the network of connecting wires and terminals. It may also indicate impedance values, frequency response information, and the routing of telephone line connections. For rotary phones, the diagram often included the complex cam and spring arrangements of the dial mechanism; for touch-tone phones, it documented the frequency-generating circuits and the arrangement of capacitors and resistors.
The term comes from the simple fact that the diagram was literally pasted into the phone during assembly. Unlike a separate service manual kept in a workshop, the paster was permanent, always there when someone cracked open the casing. This made it particularly valuable for field technicians working without reference materials nearby.
The quality and detail of pasters varied significantly by manufacturer and model era. Early telephone company pasters were often hand-drawn or printed on thin paper, while later ones became more refined photographic reproductions or professionally printed schematics. Some manufacturers were meticulous, including color coding for wire bundles and detailed component callouts; others provided minimal information, forcing technicians to rely on experience and part numbers visible on the actual components.
By the 1980s and 1990s, as phones became more compact and integrated circuitry more common, pasters became less informative and eventually less common altogether. Cordless phones and mobile devices eliminated the need for internal service diagrams entirely. However, in vintage telephone collecting and restoration, an intact, legible paster can be historically significant and invaluable for understanding original assembly and identifying component generations or manufacturing variations across production runs.